Mint Chocolate Cupcakes

INGREDIENTS

For the cupcakes:

3/4 cup

unsweetened Dutch-process cocoa powder

3/4 cup

hot water

3 cups

all-purpose flour

1 tsp

baking soda

1 tsp

baking powder

1 1/4 tsp

coarse salt

1 1/2 cups

unsalted butter

2 1/4 cups

sugar

large eggs, at room temperature

4 tsp

vanilla extract

1 cup

sour cream, at room temperature

For the filling:

8 oz

bittersweet chocolate, finely chopped

1 cup

plus 2 tbsp. heavy cream

4 tbsp

unsalted butter, cut into 4 pieces, at room temperature

1 tbsp

creme de menthe

(optional)

For the frosting:

large egg whites

1 cup

plus 2 tbsp. sugar

salt

1 lb

unsalted butter, at room temperature

2 tsp

mint extract