For the cake:
1/2 cup butter softened
1 cup granulated sugar
1 teaspoon vanilla
1-3/4 cups flour
1/2 teaspoon baking soda
1/4 teaspoon baking powder
1/4 teaspoon salt
1/2 cup sour cream
1/2 cup Champagne, prosecco, or your choice of sparkling wine
For the pastry cream:
1/2 cup heavy cream, divided
1/2 cup Champagne or prosecco
2 tablespoons cornstarch
5 tablespoons granulated sugar
1 whole egg
2 egg yolks
2 tablespoons unsalted butter
1 teaspoon vanilla
For the frosting:
1 cup plus 1 tablespoon champagne or prosecco
2 sticks of butter softened
2-1/2 cups confectioners’ sugar
Make the cupcakes: Preheat oven to 350 degrees.
In the bowl of a stand mixer fitted with the paddle attachment, cream together butter and sugar until light and fluffy. Add eggs one at a time beating well after each addition. Add vanilla and mix. Whisk together flour, baking soda, baking powder and salt, set aside. In a medium sized bowl, whisk together 1/2 cup champagne and 1/2 cup sour cream (mixture will fizz and bubble a little). Add flour and Champagne mixture alternately, beginning and ending with flour. Batter will be thick.
Fill cupcake papers with 1/4 cup level measures of batter. Bake for 17-22 minutes. Set aside.
Make the pastry cream filling: In a medium bowl, whisk cornstarch in 1/4 cup of heavy cream. Combine the remaining heavy cream, sugar and 1/2 cup Champagne in a saucepan; bring to a boil then remove from heat.
Beat the whole egg and egg yolks into the cornstarch/heavy cream mixture. Pour 1/3 of boiling champagne mixture into the egg mixture, whisking constantly so the eggs do not cook. Return the remaining Champagne/heavy cream mixture to a boil.
Pour in the hot egg mixture in a stream, whisking constantly until the mixture thickens. Remove from heat and beat in the butter and vanilla.
Cut a divot into the top of each cupcake and fill with pastry cream. Trim the cut-out cake pieces flat to make a “lid” and place on top of the filled divot.
Make the frosting: Place 1 cup of champagne in a small saucepan. Simmer over medium-high heat until reduced to 2 tablespoons. Transfer to a small bowl or condiment cup and allow to cool.
In the bowl of a stand mixer fitted with the whisk attachment, cream softened butter and powdered sugar together. Once the frosting is thick and fluffy, pour in the reduced 2 tablespoon Champagne plus 1 tablespoon Champagne from the bottle and mix well.
Frost the cream-filled cupcakes and decorate with pastel dragées.
Makes about 17 cupcakes.
Via Yum Sugar