Preheat the oven to 350°F (175°C) and line a cupcake pan with 24 liners.

Cream together sugar and butter in a mixing bowl for 3-5 minutes until fluffy.

Gradually blend in eggs, milk, and vanilla extract until smooth.

Whisk together flour, baking powder, and salt in a separate bowl.

Alternately add dry mixture and champagne to the wet ingredients, mixing until just combined.

Fill cupcake liners about two-thirds full and bake for 14-17 minutes.

Cool cupcakes on a wire rack for about 10 minutes before transferring to cool completely.

Reduce 1/2 cup of champagne in a saucepan until reduced by half, then cool.

Beat softened butter, gradually add confectioners' sugar, then mix in champagne reduction and vanilla.

Frost cooled cupcakes with champagne buttercream and add decorative sprinkles.