Fatty Crab chef Corwin Kave is living our childhood fantasy: His mom owns a candy store. Roni-Sue Kave first introduced diners to her buttercrunch at Borough Food & Drink through the good offices of Zak Pelaccio, the restaurant’s consulting chef. It was first sold at the retail counter, but now demand has put it on the menu. Kave’s store at the Essex Street Market will stock her even better fruit-flavored chocolate truffles. We had a little tasting here at the Grub Street offices, and each one was better than the last. There is none of the disgusting, cloying sweetness or gag-inducing cream innards you find in most fruit-filled chocolates. These taste like actual fruit (strawberry-rhubarb, mango) with a dark-chocolate oomph. Does Corwin have a sister? With food this good running in the family, we’ll marry her sight unseen.