Ikar and Tofel (Ikur and Tofeil)
Intro: The Mishna on Berachot 44a states that when one eats an Ikar (primary) and a Tofel (secondary) food, he only makes the beracha on the Ikar food, and that will exempt the beracha for the Tofel food.
This principle works both for the brocha rishona and for the bracha achrona. However, when it comes to the bracha achrona, one must eat at least a kazayit of the Ikar food in order to make a bracha achrona on it and cover the tofel food. In a case where one ate less than a k'zayis of the ikar food but one did eat at least a kzayis of the tofel food he would make a bracha rishona on the Ikar (mezonos) and a bracha achrona on the Tofel (bore nefashos).
are 3 different type of Ikar and Tofel scenarios: We shall go through them one by one.
Outline / Summary Chart
I. Tofel by Function (Serving Tofel or Tofeil HaMeshameshet)
Definition: is when you have two separate food items and one item serves the other item. The Tofel is not eaten for its own enjoyment, but only for the sake of the Ikar, in that sense we say the tofel serves the Ikar. Simply put: had you not eaten the Ikar, then you wouldn't eat the Tofel either.
Specific Rules of this category:
1. The Tofel item does not need to be eaten in the same bite as the Ikar item but it needs to either be present in front of you or in your mind as you make the beracha. 
2. After making the Bracha on the Ikar one must eat the Ikar first or eat the Ikar together with the Tofel, however, one should not eat the Tofel before the Ikar.
3. Even bread can be Tofel, however, using bread for this purpose is discouraged because this halacha only applies where one isn't hungry and only has intent to remove the bitterness, however, if one also intends to become satiated from the bread it is deserving of it's own Bracha but who really knows if the bread is only coming to remove a bitter taste.
4. Example: If I were to eat something sharp like whisky and I wanted to soothe the harsh aftertaste with chic peas, I would only make a beracha on the chic peas and not the cake.
Definition: If one eats two foods together where one wants to eat both items but one enhances the other the Bracha is made on the one being enhanced and it exempts the other one.
Specific Rules of this category:
1. The tofel item needs to be eaten along with the Ikar. For example, apple sauce with latkes would be considered tofel and wouldn't require its own bracha. If there is leftover applesauce it does not require another Bracha, however, if one takes more applesauce it will require a Bracha.
2. Determining which item is the Ikar is completely subjective and based on the individual.
3. Here are some examples of Tofel enhancers (first food mention is tofel, second is ikar):fruit topping on ice cream, peanut butter on rice cakes, strawberry on cake for decoration, cream on cake, cheese on crackers.
4. Mezonot is an exception to the rule and even when it is used as an enhancer one should make a Bracha on the Mezonot as well as on the primary food. This only applies to the five grain products and not rice products. However, if the mezonot is used as an absolute Tofel or is used in a non-significant manner such as where it is used in place of a cup it is exempt with the Bracha on the primary food.
Definition: If the ingredients are cooked or baked together and both ingredients are typically eaten on one spoonful it is considered a single entity. Also if the ingredients are mixed or blended so that one spoonful contains both foods it is considered a single entity. In such cases, only one bracha is made and it is upon the ikar component within the mixture.
Specific Rules of this Category:
1. The determination of the ikar component is as follows:
Exception: If the mezonot item is merely serving the other items in the mixture then it wouldn't be the ikar. If it was merely used to add color, smell, thicken, prevent sticking to the pan, or as a binding agent- then the mezonot ingredient is tofel. Since the flour in licorice (Twizzlers) is used to thicken and bind the Bracha is shehakol.
b. If there isn't any mezonos ingredient, then if one ingredient enhances the other the ikar is the ingredient that's being enhanced.
2. If neither ingredient enhances the other the majority item is ikar.
IV. Some Common Foods
Chocolate covered nut or fruit (such as peanuts or raisins) - if one really wants to eat the nut or fruit and one views the chocolate as enhancing the nut/fruit and he really wants to eat the nut/fruit - the Bracha is make on the nut or fruit (ha'etz/ha'adoma). If one really wants to eat the chocolate but the nut enhances the chocolate- then make a shehakol. If he really likes them both (1) some say to make the Bracha on the majority ingredient and if one can't determine the majority make Shehakol and (2) some say to make HaEtz except on chocolate covered peanuts which requires two Brachot (make Shehakol on chocolate covering and HaAdama when one reaches the nut).
Onion Rings / Knishes - mezonot. This is because both the onion and the mezonot batter are fried together and eaten together and thus qualifies for the third category. 
Cheese Cake - Many opinions say if the crust is used to add flavor the Bracha is Mezonot (category 3 with mezonot) and if the crust is only meant to hold the cheese the Bracha is Shehakol (because mezonot is serving other ingredient). Some say if there is a thin layer of crust used to enhance the appearance of the cake the Bracha is Shehakol, and if there is a thick layer the Bracha is Mezonot.
Cholent - if all the pieces are generally eaten in one spoonful then would only require one beracha. Assuming there is even a little barley in there - then the one beracha would be a mezonot. If the meat pieces are so big that you eat them by themselves - then make two berachos, a mezonot on the rest and a shehakol on the meat. If the potatoes are big - then make 2 berachot - mezonot on rest and ha'adoma on potatoes. 
Fruit Salad - an example of the 3rd category, even though it's not cooked since its mixed completely and you eat several pieces per forkful. Therefore make a beracha on the majority food.
Ice Cream in a Cone -If the cone enhances the taste of the ice cream, then you'll need to make two berachot, mezonot on cone and Shehakol on ice cream. If the cone is used merely to hold the ice cream - then only make a shehakol. (This is category 2 with a mezonot ingredient which depends on whether it enhances or serves.)
Ice Cream Sandwich - Since the mezonot cookie enhances the ice cream you should break off a piece of the ice cream cone and make mezonot, then make shehakol on the ice cream. (This is category 2 where the mezonot enhances.)
Frank in a Blank - mezonot. (This is category 3.)
Fried Chicken (Shnitzel) or Fish - with a thin batter coating is Shehakol, but if there's a thick coating the Bracha is Mezonot, yet it's preferable to separate off a piece of coating and a piece of chicken and make Mezonot on the coating and Shehakol on the chicken. However, the Sephardic minhag is to make Shehakol in all cases.
Corn Muffin - have wheat flour and so the Bracha is Mezonot. (This is category 3.)
Jelly Doughnut - the filling is an enhancer to dough and therefore mezonot.
Meatballs and Spaghetti - if the meatballs are small and eaten on same forkful as spaghetti only make Mezonot. However, if the meatballs are eaten separately make mezonot on spaghetti and then shehakol on meatballs. (This is category 3.)
Pancakes -mezonot. (This is category 3.)
Pie - mezonot. (This is category 3.) However, regarding Bracha Achrona if one ate a kezayit in kedi achilat pras make Al HaMichya but if one didn't but one did eat a Kezayit (in kedi achilat pras) of the all the ingredients together, according to Ashkenazim, make a Boreh Nefashot.
Licorice (Twizzlers) - shehakol since the flour is only used as a binding ingredient and therefore tofel. 
 S"A 212:1
 Vezot HaBracha (chap 11, pg 89) based on Igrot Moshe 4:42
 Halachos of Brachos (chap 4, pg 55)
 Mishna Brurah 212:5, Halachos of Brachos (chap 4, pg 55)
 S"A 204:12, Vezot HaBracha (pg 89)
 Mishna Brurah 212:5, Halachos of Brachos (chap 4, pg 54-5)
 Rama 212:1 writes that if one eats the Tofel before the Ikar the Tofel deserves Shehakol even if that's not it's original Bracha, however, many Biur Halacha D"H VeEino and Mishna Brurah 212:10 quote many achronim who argue that if one eats the Tofel first one should make the original Bracha of the Ikar. Mishna Brurah concludes that to avoid dispute one should refrain from this situation. This is quoted by Vezot HaBracha (pg 95) and Laws of Brachos (pg 227). Halachos of Brachos (pg 76) writes that one must refrain from this situation because of Bracha Sheino Tzaricha.
 Mishna Brurah 212:5 quoting the Shlah, Vezot HaBracha (pg 89), Halachos of Brachot (pg 57)
 Halachos of Brachos (pg 55). For similar examples see S"A 212:1 and Vezot HaBracha (pg 89).
 Mishna Brurah 212:6, Vezot HaBracha (pg 89), Halachos of Brachos (pg 58), Laws of Brachos (pg 209)
 Shaar HaTzion 212:21, Vezot HaBracha (pg 89). Even though the Laws of Brachos (pg 209) seems to argue on this, it clear from his examples and footnote that he's not arguing but just is using different terms than the Shaar HaTzion.
 Halachos of Brachos (pg 59-60)
 Halachos of Brachos (pg 59)
 Halachos of Brachos (pg 58), Vezot HaBracha (pg 90)
 Halachos of Brachos (pg 60-1). Vezot HaBracha (pg 90) doesn't write that mezonot is an exception to Tofel enhancers, however, he stipulates that if the Tofel enhancer is important then it requires its own Bracha.
 Aruch HaShulchan 212:1-2, Halachos of Brachos (pg 62-4), Laws of Brachos (pg 207)
 S"A 208:2, Halachos of Brachos (pg 65), Laws of Brachos (pg 217)
 S"A 208:7, Mishna Brurah 208:30, Halachos of Brachos (pg 65), Laws of Brachos (pg 216)
 S"A 208:2, Halachos of Brachos (pg 67)
 Halachos of Brachos Handbook (pg 55)
 Mishna Brurah 212:1, Halachos of Brachos (pg 67)
 Mishna Brurah 212:1, Halachos of Brachos (pg 68)
 Laws of Brachos (pg 215), Halachos of Brachos (pg 417), Vezot HaBracha (pg 96)
 Vezot HaBracha (pg 96)
 Laws of Brachos (pg 215)
 Laws of Brachos (pg 294, 375), Halachos of Brachos (pg 79)
 Laws of Brachos (pg 219). Vezot HaBracha (pg 92) seems to agree.
 Halachos of Brachos (pg 79)
 Halachos of Brachos (pg 80)
 Laws of Brachos (pg 364), Halachos of Brachos (pg 80), Vezot HaBracha (pg 392)
 Vezot HaBracha (pg 94)
 Laws of Brachos (pg 370), Vezot HaBracha (pg 390), Halachos of Brachos (pg 61)
 Halachos of Brachos (pg 72), Laws of Brachos pg 370)
 Halachos of Brachos Handbook (pg 51)
 Halachos of Brachos Handbook (pg 13 and 43), VeZot HaBracha (chap 12, pg 109)
 Yalkut Yosef (Brachot (vol 3), pg 426)
 Halachos of Brachos (pg 502), Laws of Brachos (pg 365)
 Halachos of Brachos Handbook (pg 38)
 Halachos of Brachos Handbook (pg 59)
 Halachos of Brachos (pg 492)
 Halachos of Brachos (pg 504-5)
 Halachos of Brachos Handbook (pg 70)
 Halachos of Brachos Handbook (pg 55)