Make the vanilla cupcakes:

1. Preheat your oven to 350°F. Line 2 standard sized cupcake tins with 16 paper liners and set aside. *(see notes for using 1 cupcake tin)
2. In a medium bowl, whisk together flour, baking powder, baking soda, and salt to combine. Set aside.
3. In a large bowl, combine butter, oil, and sugar. Whisk together until pale and fluffy.
4. Whisk eggs into the butter mixture one at a time, followed by the vanilla extract.
5. Mix about half of your dry ingredients in until almost completely combined - a few streaks are fine! Add sour cream and milk and whisk to combine. Finish off with the remaining dry ingredients and mix until the dry streaks just disappear. Take care not to overmix!
6. Divide the cupcake batter into your prepared cupcake cups, filling each one no more than 2/3 of the way full.
7. Bake the cupcakes in the center of your preheated oven for 15 to 20 minutes or until a skewer inserted into the center of a cupcake comes out clean.
8. Cool the cupcakes for 5 to 10 minutes in the tin, then transfer to a wire rack and set aside until cooled completely before frosting.

Make the vanilla buttercream:

1. *Note: If you like a lighter layer of frosting on the cupcakes, feel free to halve this recipe.
2. In a large bowl, combine butter and about half of the powdered sugar. Use an electric mixer fitted with the paddle attachment to mix together on low speed until the sugar is dissolved. Add the remaining sugar and mix again on low speed to dissolve.
3. Add salt, vanilla, and 4 tablespoons of milk. Whip on high speed for 1 to 2 minutes or until smooth and fluffy. If the frosting is too thick, gradually whisk in more milk 1 tablespoon at a time to reach your desired consistency. If it's too soft, add in more powdered sugar.
4. Pipe or spread the frosting onto your cooled cupcakes. Top with sprinkles if desired, then dig in!