Preheat oven to 325°. Line two cupcake pans with paper liners. Set aside.
Open champagne bottle and measure out 1¼ cups of champagne. Place in a saucepan and simmer on medium for 6-8 minutes and let it reduce to about ⅔ cup of liquid. Let this liquid cool to room temperature before mixing in with the batter. Reserve about 2-3 tablespoon for the buttercream frosting.
In a small mixing bowl, whisk together the cake flour, baking soda, and salt. Set aside.
In a large mixing bowl and with an electric mixer, mix together the butter and vanilla extract until smooth and creamy. Add in the sugar, vegetable oil and eggs and mix until well combined.
Alternating the flour mixture with the champagne reduction, slowly add to the butter mixture. Starting and ending with the flour mixture. Scrape down the sides of the bowl as needed.
Transfer batter to prepared cupcake liners and fill to about ⅔ to ¾ full and bake for 18-20 minutes or until toothpick inserted inside comes out clean. Cool completely before frosting.
Pink Champagne buttercream
In a bowl of a stand mixer fitted with a paddle attachment, mix the butter on medium until light and fluffy. Slowly add in the confectioner's sugar until combined. Add in the champagne reduction, vanilla, and salt and mix until combined. Add heavy cream as needed or until desired consistency has been reached.
Pipe and frost cupcakes as desired. Sprinkles can be added and are optional.