Preheat oven to 350 F and like 24 standard sized cupcake tins with paper liners.
Sift together cocoa, flour, baking powder, and salt. Set aside.
In a large mixing bowl, cream together butter and sugar until light and fluffy. Beat eggs in one at a time, then beat in the vanilla.
Decrease the mixer's speed to low, then begin adding the sour cream and flour. Start with some flour, switch to some of the sour cream, switch back to flour, etc, and continue alternating until all has been mixed in.
Divide the batter between the paper cups, filling each about 3/4 full. Bake until they pass the toothpick test, about 20 minutes.
Remove from oven and let cool completely before topping.
Once the cupcakes have cooled, use a piping bag or butter knife to distribute the pastry cream between the cupcakes. Place a meringue chick on each, revel in the cuteness, and enjoy!