Step 1: Brown the Butter - Melt 2 cups of unsalted butter in a saucepan over medium heat, stirring frequently until golden brown and nutty in aroma.

Step 2: Prepare the Cupcake Batter - Combine ¾ cup of cooled brown butter with sugars, beat until fluffy, then add eggs, vanilla, sour cream, and milk.

Step 3: Mix Dry Ingredients - Whisk flour, baking powder, and salt then fold into wet mixture until just combined.

Step 4: Add Chocolate Chips - Fold in mini chocolate chips evenly into the batter.

Step 5: Bake the Cupcakes - Preheat oven to 350°F (175°C), fill cupcake liners ⅔ full with batter, and bake for 20-22 minutes.

Step 6: Make Ganache Filling - Heat cream until simmering, pour over chocolate and butter, let sit a minute, then stir until smooth.

Step 8: Make the Frosting - Beat remaining brown butter with cream cheese, add powdered sugar gradually until combined.

Step 9: Assemble the Cupcakes - Create a well in cooled cupcakes, fill with ganache, frost with cream cheese frosting, and top with a mini cookie.