best quality dark, milk or white
, about 3 1/2 cups coarsely chopped
sweetened condensed milk
To make Classic Chocolate Fudge:
Line the bottom and sides of an 8 × 8-in. pan with 2 large overlapping pieces of plastic wrap, letting wrap hang over sides of pan.
Combine chocolate and milk in a large microwave-safe bowl. Microwave, uncovered, on medium, stirring halfway through, until chocolate is almost melted, 3 to 4 min. Remove and stir until evenly mixed and smooth. Scrape mixture into prepared pan and press down, smoothing top. Fold overhanging ends of plastic wrap over fudge to completely cover. Refrigerate at least 2 hours or overnight. Fudge keeps well, refrigerated, up to 1 week.
To make Molten Cakes:
Prepare cake batter for 12 cupcakes. Pour batter halfway up cups of a muffin tin. Lay a piece of Classic Chocolate Fudge in the middle and cover with remaining batter. Bake as directed. Serve warm.