Preheat the oven to 350°F degrees. This recipe makes 12-14 cupcakes, so prepare one pan (or maybe two) with cupcake liners.

Melt the butter and chocolate together in the microwave. Microwave in 30-second increments, stirring in between each time. Set aside.

In the bowl of a stand mixer with the whisk attachment, add the eggs, sugar, vanilla, and sour cream and whisk on medium speed until smooth. (about 1 minute)

In a medium-sized bowl, sift the cocoa powder, flour, baking soda, baking powder, and salt together until thoroughly combined.

Add the cooled butter/chocolate to the stand mixer and whisk until smooth, about 30 seconds.

Slowly add in the flour mixture, about 1/4 cup at a time with the stand mixer on low.

As soon as you are done adding the flour turn the mixer off. (You do not want to over-mix!)

The batter will be very thick.

Fill the cupcake liners 2/3 of the way full with batter. Bake for 15-18 minutes. The center of the cupcake should spring back up if gently pressed.

In the bowl of an electric mixer, beat butter until light and smooth.

Fold in Oreo crumbs, mix until smooth. (reserve some for topping)

Add milk 1 tablespoon at a time, until you get the consistency you desire.