1 1/4 cups unbleached, all-purpose flour
2 teaspoons baking soda
2 teaspoons baking powder
1/4 teaspoon coarse salt
1 1/4 cups granulated sugar
4 ounces unsweetened chocolate, chopped
1 stick unsalted butter, cut into pieces
2 teaspoons pure vanilla extract
2 large eggs, lightly beaten
Filling
4 tablespoons unsalted butter, at room temperature
1 cup powdered sugar
2 teaspoons pure vanilla exrtact
3 tablespoons heavy cream
1 cup marshmallow creme
Ganache
6 ounces bittersweet chocolate, chopped
1/2 cup heavy cream
1 tablespoon unsalted butter
2 teaspoons pure vanilla extract
Icing
1 stick unsalted butter
1 1/2 - 2 tablespoons milk
2 cups powdered sugar
1/4 tsp vanilla
Place oven rack in the center of the oven and preheat to 350. Place paper liners in muffin tin for about 20 cupcakes.
Cupcakes
Place sugar and 1 cup of water in a saucepan. Bring to a boil, stirring until the sugar dissolves, about 3 minutes. Pour into a large bowl. Add the chocolate and butter and let sit, stirring occasionally, until the chocolate is melted and the mixture has cooled slightly. Stir in the vanilla.
Sift together the flour, baking soda, baking powder and salt in a bowl.
Beat the eggs into the chocolate with a mixer, then stir in the dry ingredients.
Divide the batter evenly between the prepared pans (~1/4 cup batter per cupcake) and bake until a toothpick inserted in the center comes out clean, about 20-25 minutes. The cupcakes will sink in the middle slightly. Cool in the pans for 25 minutes, then transfer to a rack and cool completely.
Filling
While cupcakes are cooling, make the filling. Using a mixer, cream the butter until light and fluffy. Beat in 1/2 cup confectioners’ sugar. Add the vanilla and 1 tablespoon heavy cream and beat until smooth. Alternating between batches, beat in the remaining 1/2 cup confectioners’ sugar and 2 tablespoons heavy cream. Beat in the marshmallow creme. Refrigerate until ready to use.
Ganache
Place the chocolate in a stainless-steel bowl. Heat the cream and 1 tablespoon butter in a saucepan until just boiling, then pour over the chocolate. Let stand for 5 minutes. Whisk until smooth. Add 2 teaspoons vanilla; let stand until cool but still glossy and liquid.
To Assemble
Spoon the filling into a pastry bag with a medium star tip. Insert the tip into the center of each cupcake top; fill until the cupcake is heavier (do not overfill). It's OK if some of the filling peeks out, it will be covered by the ganache. (I thought this part would be complicated and I was worried, but it was fine. I had Mike test one of the cupcakes to make sure I had the right amount of filling in it.)
Spoon a little ganache on each cupcake and lightly spread with an offset spatula or a knife. Chill for at least 15 minutes.
Meanwhile, prepare the icing: Using a mixer, beat the remaining 1 stick butter, 1/4 teaspoon vanilla, milk and confectioners’ sugar until smooth, adding more milk if needed. Spoon into a pastry bag with a small tip. Pipe onto the cupcakes to decorate.
Store cupcakes in the refrigerator.