Preheat the oven to 325 degrees F and line a cupcake pan with liners.
In a medium bowl, whisk together the flour, cocoa powder, baking powder, and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter and sugar for 2-3 minutes until light & fluffy.
Mixing on low speed, add the eggs one a time.
Scrape down the bowl and mix in the vanilla.
Add half of the dry ingredients and mix until just combined.
Mix in the sour cream and oil.
Add the rest of the dry ingredients and mix until just combined.
Scrape down the bowl to ensure everything is evenly incorporated.
Fill the cupcake pan by adding 5 tablespoons of batter to each cup.*
Smooth out the batter with a spoon and tap the pan on the counter a few times to release any air bubbles.
Bake the cupcakes for about 22-25 minutes or until a toothpick inserted comes out clean.
Allow the cupcakes to cool in the pan for a few minutes before transferring to a wire rack to cool completely.