Preheat your oven to 350°F (175°C) and line a muffin tin with cupcake liners.
In a bowl, cream together the softened butter and granulated sugar until light and fluffy.
Add the eggs one at a time, beating well after each addition, then stir in the vanilla extract.
In a separate bowl, whisk together the flour, salt, and baking powder.
Gradually add the dry ingredients to the creamed mixture alternately with the champagne, starting and ending with the dry ingredients.
Spoon the batter into the prepared muffin tin, filling each liner about two-thirds full.
Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted in the center comes out clean.
Once baked, remove the cupcakes from the oven and let them cool in the tin for 5 minutes before transferring to a wire rack to cool completely.
While the cupcakes cool, prepare the champagne buttercream frosting by beating the heavy cream until stiff peaks form.
Gradually add the powdered sugar, mixing until well combined and then stir in the champagne.
Once the cupcakes are completely cool, frost them generously with the champagne buttercream.