Magic Middles - I don't know who remembers these cookies from Keebler that were in production from the late 80s to mid 90s, but they were some of my favorite cookies ever made. The middles were sort of ganache-like. I even remember my mom sending me boxes of them in some of my early college care packages.
Cake Fillings - While I am a frosting girl, I always like to see what kind of fun filling is waiting for me in the middle of a layer cake. I'm immediately reminded of some of the custom special occasion cakes we've ordered from Disney over the years and the fun fillings we requested. My two favorites...the Belle cake with passionfruit mousse filling in the middle and a Mickey celestial themed cake with two different fillings in the middle...raspberry mousse and cheesecake mousse.
Baklava - All of that honey and nutty goodness found in between the buttery layers of phyllo dough.
Honorable mention to all of the other yummy options with filling in the middle...like cannoli, filled donuts (especially Shipley's devils food with chocolate cream and lemon curd filled), King Cakes with veins of yummy fillings running through the middle, and all of the choux dough creations like profiteroles and eclairs. Then we've got the stuffed category with fillings in the middle...like calzones, stromboli, spanikopita, tiropita, epanadas, ravioli, knish, pierogi, kreplach. Let's also not forget the cookies (both with fillings in the middle and ones where that filling in the middle gives you a little sneak peak in the center)... Italian sandwich cookies, ischler, linzer, hamentaschen, and even the many varieties of Oreos (double stuffed mint dipped in chocolate!!!).