Preheat the oven to 350F. Line cupcake pans with 18 paper liners and set aside.

In the bowl of an electric mixer, beat the egg whites to stiff peaks; set aside.

In another bowl of an electric mixer, beat together the butter and sugar until light and fluffy.

In a separate bowl, sift together the flour, baking powder, and salt. Whisk to combine.

Add the flour mixture to the creamed butter mixture alternately with the champagne. Stir in the chopped peaches.

Fold 1/3 of the egg whites into the batter until incorporated. Then, fold in the remaining egg whites.

Spoon the batter into the prepared cups. Bake for 18-22 minutes, or until a toothpick inserted near the center comes out clean. Cool for 5 minutes in the pan, then transfer the cupcakes to a wire rack to cool completely.

In a medium bowl, whisk together 1/4 cup of the heavy cream and the cornstarch. Whisk in the whole egg and egg yolks; set aside.

In a saucepan, combine the remaining heavy cream, sugar, and champagne. Bring to a boil then remove from heat. Pour 1/3 of the hot champagne mixture into the egg mixture, whisking constantly to prevent cooking the eggs. Return the remaining champagne mixture to a boil.

Pour in the hot egg mixture in a stream, whisking constantly until thickened. Remove from heat, stir in butter and vanilla. Let cool to room temperature; cover and refrigerate until ready to use.

In the bowl of an electric mixer fitted with the whisk attachment, beat together the butter and confectioners’ sugar. Add milk or cream until light, fluffy, and of piping consistency. Add peach flavor and beat again until incorporated. Add food color to achieve desired hue.

Fit a disposable piping bag with a large French pastry tip. Paint the inside of the bag with red food color for decoration. Set aside.

Core the cupcakes by cutting a small divot in the centers. Fill each with 1 1/2 to 2 tablespoons of pastry cream, then place the cut-out cake pieces back on top.

Pipe frosting onto each cupcake and sprinkle with white nonpareils. Optionally, add a fresh mint leaf before serving.