Prepare CHOCOLATE BAR FILLING, Beat cream cheese, sugar, egg and salt in small bowl until smooth and creamy. Stir in chocolate bar pieces.
Heat oven to 350°F. Line muffin cups (2-1/2 inches in diameter) with paper bake cups.
Stir together flour, sugar, cocoa, baking soda and salt in large bowl. Add water, oil, vinegar and vanilla; beat on medium speed of mixer 2 minutes. Fill muffin cups 2/3 full with batter. Spoon 1 level tablespoon FILLING into center of each cupcake.
Bake 20 to 25 minutes or until wooden pick inserted in cake portion comes out clean. Remove from pan to wire rack. Cool completely. Top each cupcake with chocolate bar piece. About 2-1/2 dozen cupcakes.