For the cupcakes:

1. Preheat oven to 400 degrees F. Line a 12-cup standard muffin tin with paper liners.

2. In a small microwave-proof bowl, combine the butter pieces and chocolate chips. Microwave on high for 30 seconds and stir until both chocolate and butter are fully melted, combined, and glossy. If needed, microwave once or twice more for 10 seconds. (This can also be done on the stovetop with a double boiler or glass bowl set over a pot of simmering water) Set mixture aside to cool. 

3. In a medium bowl, whisk together the flour, cocoa powder, baking soda, baking powder, and salt. Set aside. 

4. In a separate bowl, whisk together sugar, vanilla and oil until the mixture is the texture of wet sand. Whisk in the eggs one at a time, then add the butter/chocolate mixture and mix thoroughly. 

5. Add half the buttermilk to the sugar mixture and mix until combined, then add half the dry mixture, stirring until just combined with no pockets of flour. Repeat with remaining buttermilk and dry mixture, mixing just until the batter is fully combined. Overmixing will result in a tougher cupcake. 

6. Using a large cookie scoop or spoon, fill the paper liners 3/4 full. Bake at 400 degrees for 5 minutes, then reduce the temperature to 350 degrees and bake an additional 13-15 minutes, until a cake tester comes out clean and the tops of the cupcakes spring back to the touch. Avoid overbaking, which can lead to dryness.

7. Allow the cupcakes to cool in the pan (make sure they’re fully cooled before frosting). 

For the buttercream:

1. In a stand mixer fitting with either the paddle or whisk attachment, or using a handheld mixer, whip the butter for a minute or two.

2. Scrape down the bowl and add 2.5 cups of powdered sugar along with the cocoa, salt, vanilla, and milk or cream. Mix on low until all ingredients are incorporated, then increase speed to med-high and continue to whip until the frosting is light and fluffy. If the mixture seems too loose, add a little more powdered sugar; if it’s too thick, add a splash of cream. 

9. Use a piping bag to pipe frosting onto fully cooled cupcakes, or simply spread on with a knife or spoon. 

If you have cupcakes that won’t be consumed immediately, store in an airtight container and frost when ready to eat. Frosting can be stored in an airtight container in the refrigerator for up to a week. When ready to use again, bring to room temperature and whip slightly before use.