1. Heat oven to 350 degrees . Line 48 indents of mini muffin pans with paper or foil liners. If you have only 1 or 2 pans, bake batter in batches.Cupcakes
2. Place chocolate in a small glass bowl. Microwave for 45 seconds, stir and microwave for 45 seconds more. Stir until smooth; set aside to cool slightly. In a medium bowl, whisk flour, cocoa, baking powder and salt.
3. With a hand mixer, beat butter until smooth. Beat in sugar until fluffy, then beat in melted chocolate. Beat in eggs, one at a time, beating well after each. On low speed, beat in half the flour mixture, followed by sour cream mixture and remaining flour mixture. Add vanilla.
4. Transfer batter to a large resealable plastic bag and snip off a corner. Pipe into cupcake liners. Bake at 350 degrees for 14 to 15 minutes; cool completely.Frosting
5. While cupcakes are baking, microwave heavy cream for 1 minute, until steaming. Pour over chocolate in a bowl and whisk until smooth. Refrigerate for 15 minutes or until fairly cool. Beat on medium-high speed until thickened and good spreading consistency (about 5 minutes; frosting will be the color of milk chocolate). Transfer to a piping bag fitted with a small star tip and pipe frosting onto mini cupcakes (alternately, spread frosting onto cupcakes). Decorate with chocolate sprinkles.