Preheat oven to 350 degrees F/180 degrees C. Place muffin cups on a baking sheet about 2-inches apart.
Add butter and granulated sugar to the bowl of an electric mixer fitted with the paddle attachment; mix on medium speed until pale and fluffy, about 3 minutes. Add egg whites, milk, vanilla extract, and vanilla bean paste; mix until combined, scraping down sides of bowl as needed. Add flour, baking powder, and salt; mix until just combined.
Use a spatula to fold in the sugar confetti.
Divide batter among paper baking cups using a small ice-cream scoop, filling each cup about ¾ full. Bake in preheated oven until very light golden brown, approximately 24-27 minutes. Transfer pan to a wire rack; let cool completely.
To make the whipped topping:
Chill a metal bowl along with the whisk attachment of a stand mixer or hand mixer, by placing them in the freezer for 5 minutes. Remove from freezer and add whipping cream to the bowl. Sift the confectioner’s sugar onto the cream and whisk until soft peaks form. Add the champgne and whisk until peaks are stable, but not overly stiff.