Pour the champagne or sparkling white grape juice into a medium saucepan. Cook over a medium-low heat until you have a recduction of ¾ cup remaining. Be sure not to boil. Refrigerate until cool.
Preheat oven to 350° and prepare a cupcake pan with 12 cupcake liners.
Combine the flour and baking powder in a medium-sized bowl and set aside.
Place butter, sugar and oil in a large mixing bowl and beat until light and fluffy.
Add the eggs one at a time, mixing after each until combined. Add in the vanilla extract with the second egg and mix. Scrape down the sides of the bowl often.
Add half of the dry ingredients and mix until combined.
Add the milk and champagne reduction and mix until thoroughly incorporated.
Add the remaining dry ingredients and mix until well combined and smooth. Be sure not to overmix the batter.
Fill the cupcake liners about ¾ full and bake for approximately 15 minutes, or until a toothpick inserted in the center comes out clean. Remove to cooling rack to cool completely.