PREHEAT oven to 350º F. Paper-line 18 muffin cups.
MICROWAVE chocolate in small, uncovered, microwave-safe bowl on MEDIUM-HIGH (70%) power for 45 seconds; STIR. If pieces retain some of their original shape, microwave at additional 10- to 15-second intervals, stirring just until melted. Cool to room temperature.
COMBINE flour, baking soda and salt in small bowl. Combine milk and vinegar in small glass measure. Beat sugar, oil, eggs and vanilla extract in large mixer bowl on high for 2 minutes. Carefully beat in melted chocolate and red food coloring. Gradually beat in flour mixture alternately with milk mixture. Spoon into prepared muffin cups, filling 2/3 full.
BAKE for 22 to 27 minutes or until wooden pick inserted in centers comes out clean. Cool in pan for 10 minutes; remove to wire racks to cool completely. Frost with Cream Cheese Frosting. Top with sprinkles, if desired.
FOR CREAM CHEESE FROSTING:
BEAT cream cheese, butter, milk and vanilla extract in medium mixer bowl until light and fluffy, scraping bowl occasionally. Gradually beat in powdered sugar until light and fluffy. Makes about 1 3/4 cups.
• You may substitute store bought cream cheese frosting (one 16-oz. container) to save time.
• Frosting can be piped on with a pastry bag for a professional look.