Preheat the oven to 350°F (175°C). Line 12 cupcake cups with cupcake liners.
In a medium bowl, whisk together flour, baking powder, baking soda and salt. Set aside.
In a large mixing bowl, beat the egg whites until soft peaks form.
In another large mixing bowl, beat butter and sugar until fluffy, at least 3 minutes.
Stir in half of the flour mixture, followed by champagne, and then add the remaining dry ingredients. Mix until mostly combined. (Don’t overmix it.)
Fold in half of the whipped egg whites into the batter, then add remaining egg whites and gently mix until no egg whites visible.
Using a large cookie scoop, divide the batter into 12 cupcake cups. (Cups should be 2/3 way full.) Bake for 15-18 minutes, or until inserted toothpick comes out clean. Cool in the baking tin for about 10 minutes and then transfer onto the wire rack to cool completely.