Brown your butter. Place 2 cups of unsalted butter in a light colored saucepan over medium heat. Let it melt completely, then keep stirring as it foams and bubbles. The butter will go from yellow to golden to amber, and you will start to see little brown bits on the bottom of the pan. When it smells nutty and toasted (about 6 to 8 minutes total), pull it off the heat IMMEDIATELY. Pour into a heat safe bowl, scraping in all those brown bits, and let cool for 5 to 10 minutes.

Preheat oven to 350°F and line a cupcake pan with 12 liners. Have a baking sheet ready for the mini cookies later.

Make the cupcake batter. In a stand mixer, beat 3/4 cup of the cooled brown butter with the light brown sugar and granulated sugar on medium speed until fully combined and fluffy, about 2 minutes. Add the eggs one at a time, beating well after each, then mix in the vanilla extract.

Add the sour cream and milk (or buttermilk) and mix until just combined. The batter will look a little broken at this stage, that is totally normal.

In a separate bowl, whisk together the flour and baking powder. Slowly fold this into the wet ingredients until JUST combined, do not overmix or you will get tough cupcakes. Fold in the mini chocolate chips.

Scoop the batter into the cupcake liners, filling each about 3/4 full. Bake at 350°F for 20 to 22 minutes, or until a toothpick inserted in the center comes out clean. Let cool in the pan for 5 minutes, then transfer to a wire rack to cool COMPLETELY.

While the cupcakes bake, make the ganache. Place the chopped chocolate (or chips) and 2 tbsp butter in a heat safe bowl. In a small saucepan, heat the heavy cream until it is JUST lightly simmering, do not boil. Pour the hot cream over the chocolate and butter and DO NOT TOUCH IT for 2 to 3 minutes. Then stir slowly from the center out until smooth and glossy. Set aside to cool and thicken at room temperature.

Make the mini chocolate chip cookies. In a bowl, mix together 3 tbsp cooled brown butter, the light brown sugar, and the granulated sugar until combined. Add the egg yolk and vanilla extract and mix again. In a separate bowl, whisk the flour, baking powder, and cornstarch, then fold into the wet ingredients. Fold in the mini chocolate chips.

Scoop 12 small cookies (about 1 tablespoon each) onto a baking sheet and FREEZE for 10 minutes. Bake at 350°F for 8 to 10 minutes, until the tops are just set and lightly crisp on the edges. You want these slightly more crisp than your usual chewy cookie because they are going to act as a crunch factor on top of the frosting. Cool completely on the pan.

Make the frosting. In a stand mixer, beat together 4 tbsp cooled brown butter, the cream cheese, and the brown sugar until smooth and fluffy, about 2 to 3 minutes. Add the vanilla extract, salt, and heavy cream. Slowly add the powdered sugar 1/2 cup at a time, beating until you reach a thick but pipeable consistency.

Assemble. Make sure your cupcakes are COMPLETELY cool. Use an apple corer or small paring knife to poke a hole in the center of each cupcake, going about halfway down. Fill each hole generously with the ganache. Pipe the frosting on top in a generous swirl, then crown each cupcake with a mini chocolate chip cookie. Serve immediately or refrigerate until ready to serve.