Preheat your oven to 350°F (175°C) and line a cupcake pan with paper liners.

Whisk together flour, baking powder, and salt until well combined.

Beat the softened butter and sugar together until light and fluffy, about 2-3 minutes.

Add eggs, one at a time, mixing well after each addition.

Whisk together champagne, milk, vanilla extract, and peach puree until blended, then combine with the butter and egg mixture.

Gradually add the dry ingredients to the wet mixture, mixing on low speed until just combined.

Fill cupcake liners about two-thirds full with battery and bake for 18-20 minutes.

Cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.

Beat butter until smooth, then gradually add powdered sugar, peach puree, champagne, and salt to make the frosting.

Frost each cooled cupcake with the peach buttercream using a piping bag or knife.

Garnish with fresh peach slices and a sprinkle of sparkling sugar before serving.