Beat the butter and oil together. Stream in the granulated sugar and mix until fluffy. Add the eggs one by one and mix until combined. Add the vanilla extract and mix.
Add half of the dry ingredients. Once almost fully incorporated, add half of the milk and mix until almost combined. Repeat this with the other halves of the dry ingredients and the milk.
Divide the batter evenly amongst the cupcake cups. Bake the cupcakes for 16-18 minutes at 350 degrees Fahrenheit until a toothpick inserted into the center of the cupcake comes out clean.
Beat the butter by itself for 1-2 minutes until smooth and creamy. Add the powdered sugar, salt, vanilla extract and milk/heavy cream and beat until combined.
Once the cupcakes are completely cool, frost and enjoy!