In the coming days, we hope to provide several important points in the laws of Brachos, for it is not only essential to make Brachos with Kavannah, but also to make the appropriate brachos, as well. The following is an excerpt from the Halachos of Brachos Handbook (Feldheim, p. 33), by Rabbi Yisroel Pinchos Bodner, Shlita.
"Crackers with Cheese or Tuna: The Poskim write that when crackers are eaten with another food (e.g., cheese or tuna), the other food is often used [merely] to enhance the crackers, in which chase a Mezonos on the crackers will cover the other food, as well. However, if the other food is not being eaten [merely] to enhance the cracker, two brachos are required (e.g., he enjoys both the tuna and the crackers equally, but he eats them together because he enjoys the way they taste together). First, one should make a Borei Minei Mezonos and eat some cracker, and then make a Shehakol and eat some tuna [or cheese]. Each of the two foods then requires their respective Brocha Achrona, if the shiur of each is eaten."
Likewise, The Laws of Brachos, by Rabbi Binyomin Forst (Artscroll, p. 222-223), writes that if one desires to eat jam or peanut butter, independent of the cracker, two Brachos must be said. Additionally, one who uses a bland-tasting cracker merely to hold the jam or peanut butter recites no brocha on the cracker, which is being used in the place of a spoon or fork, and not for food purposes, and thus loses its status completely.
Hakhel Note: The two-brachos ruling would apparently also apply to one who, at a Kiddush, places a piece of herring on a flat cracker (kichel), in a situation where he really wants to eat the herring, as well, and puts it on the kichel because he enjoys the taste of the two of them together. As with all other matters, one should consult with his Rav or Posek for a final Písak.