COMBINE flour, cocoa, baking soda and salt in small bowl. Beat sugar, butter, eggs and vanilla extract in large mixer bowl. Gradually beat in flour mixture alternately with milk. Spoon 1/4 cup batter into each prepared muffin cup.
BAKE for 18 to 20 minutes or until wooden pick inserted in centers comes out clean. Cool in pans for 5 minutes; remove to wire racks to cool completely. Frost with Milk Chocolate Frosting.
FOR MILK CHOCOLATE FROSTING:.
MICROWAVE morsels, butter and salt in medium, uncovered, microwave-safe bowl on MEDIUM-HIGH (70%) power for 1 minute; STIR. The morsels may retain some of their original shape. If necessary, microwave at additional 10- to 15-second intervals, stirring just until morsels are melted. Transfer to large mixer bowl. Gradually beat in sugar alternately with milk. Stir in vanilla extract.