1. Prepare Oven and Liners:

• Preheat the oven to 350°F (175°C).
• Line a standard 12-cup muffin pan with cupcake liners. Set aside.

2. Make the Brownie Batter:

• Add the 10 tablespoons of salted butter and the chopped semi-sweet chocolate baking bar to a medium microwave-safe bowl.
• Heat in 30-second intervals, stirring well after each interval, until the butter and chocolate are completely melted and the mixture is smooth.
• Stir the granulated sugar and tightly packed light brown sugar into the melted chocolate mixture until combined.
• Stir in the room temperature eggs, one at a time, mixing well after each addition until fully incorporated.
• Stir in the 2 teaspoons of pure vanilla extract.
• Add the all-purpose flour (½ cup + 2 tbsp) to the bowl. Stir gently with a spatula or spoon just until the flour is combined. Be careful not to overmix the batter.
• Gently fold in the 1¼ cups of milk chocolate chips.

3. Fill Liners and Bake:

• Divide the thick brownie batter evenly among the lined muffin cups, filling each about two-thirds full.
• Place the muffin pan in the preheated oven. Bake for 22 to 25 minutes.
• The cupcakes are done when a toothpick inserted into the center comes out with a few moist crumbs attached (like a fudgy brownie), but not wet batter.
• Carefully remove the muffin pan from the oven and place it on a wire rack. Allow the cupcakes to cool completely in the pan before attempting to frost them.

4. Make the Peanut Butter Frosting:

• While the cupcakes cool, prepare the frosting. Ensure the ⅔ cup butter is properly softened.
• Using either a stand mixer fitted with the paddle attachment or a medium-sized mixing bowl and a handheld electric mixer, beat together the creamy peanut butter, softened butter, and 1 teaspoon pure vanilla extract on medium-high speed for 1 to 1½ minutes, until smooth and combined. Scrape down the bowl.
• Reduce the mixer speed to low. Gradually add the sifted powdered sugar, about ½ cup at a time, alternating with adding a tablespoon of the heavy cream (e.g., Sugar-Cream-Sugar-Sugar…). Mix on low until each addition is incorporated.
• Once all the powdered sugar and cream are added, increase the mixer speed to medium-high and whip for 2 minutes until the frosting is light, fluffy, and smooth.

5. Frost and Garnish the Cupcakes:

• Ensure cupcakes are completely cool.
• Fill a piping bag fitted with an open star tip (like Wilton 1M) or a gallon-size Ziploc bag with the corner snipped off with the peanut butter frosting.
• Hold the tip about ½ inch above the surface of a cooled cupcake. Use steady, even pressure to gently squeeze the frosting in a spiral pattern, starting from the outside edge and working inwards and upwards to create a classic swirl. Repeat for all cupcakes.
• Sprinkle the crushed Butterfinger candy generously over the frosted cupcakes.
• Gently press a halved fun-size Butterfinger candy (or a larger chunk) decoratively into the top of the frosting on each cupcake.

6. Serve:

• Serve the Butterfinger Brownie Cupcakes immediately or store them in an airtight container. Enjoy the decadent combination!