Introduction to the Halachos of "Ikar and Tafel", a complicated topic which we will try to cover as best as we can. Obviously, it will be impossible for us to cover every intricate detail of this topic, so if there are any details that need further explanation please feel free to contact me and I will try my best to clarify. For Halacha L'Ma'aseh, as always, a Rav should be consulted.
The Mishna (Brachos 44a) teaches us a rule that whenever 2 food items are eaten, if one of the items is secondary to the other, the Bracha is only recited on the main food and it exempts the secondary food even if its Bracha is different. This is referred to in Halacha as "Ikar" (the main food) and "Tafel" (The secondary food) (See Shulchan Aruch beginning of Siman 212. Regarding the mechanics of how and why this works which is a subject of debate amongst the Poskim, see Chazon Ish Orach Chaim Siman 27:9, Shu"t Igros Moshe Orach Chaim Vol. 4 Siman 42, Shu"t L'Horos Noson Vol. 4 Siman 10, Shu"t Avnei Nezer Siman 38:13 and Shu"t Teshuvos V'Hanhagos Vol. 3 Siman 69)
The above is determined based on whether it is accepted by most average people in the society that one belongs to eat the two items together, and not by taking two distinct food items which aren't usually eaten together and saying "I want this to be secondary to that", as being a secondary food is not decided by each individual person. Of course if the second food is "totally secondary" (Tafel Gamur) and indistinguishable, and is actually part of the first food, then it won't be dependent on society. We will discuss this all at length iy"H over the next few days". ( See Shu"t Halachos Ketanos Vol. 1 Siman 66)
1)When reciting a Bracha on the Ikar, no special Kavanah is needed to exempt the Tafel, as anything that is totally secondary is exempt from the Bracha automatically. (See Pri Megadim Mishbetzos Zahav 212:3 where he discusses if it is possible to specifically have in mind that the Bracha on the Ikar NOT work for the Tafel.)
However, if the Tafel is being eaten to enhance the Ikar, but is not mixed into the Ikar and isn't necessarily eaten at once with the Ikar, then only with the following conditions is it exempt with the Bracha of the Ikar:
a)The Tafel is in front of you at the time of the Bracha
b)When reciting the Bracha on the Ikar you had in mind to eat the Tafel
c)It is usual to eat these 2 foods together.
d)You were Kovea Seuda (intended to eat a meal) with the Ikar, which isn't possible with drinks and fruits (See Mishna Berura Siman 212:4 and Shulchan Aruch HaRav 212:10 and 206:9)
2) If after eating the Ikar one left the location and only ate the Tafel in a new location, a new Bracha is required on the Tafel (unless the Ikar is something that requires going back to the original location for Birchas HaMazon or Al HaMichya) (see Shulchan Aruch HaRav Siman 212:11, Mishna Berura ibid, Kaf HaChaim 212:13 and Chazon Ish Orach Chaim Siman 27:9)
Likewise, if one made an interruption between the two foods, and his/her mind was not on the eating anymore (Hesech HaDa'as) a new Bracha is required on the Tafel. (See Shulchan Aruch HaRav Siman 179:2)