- 8 ounces semisweet or bittersweet chocolate, finely chopped
- 1 cup (2 sticks) unsalted butter, room temperature, cut into pieces
- 2 cups firmly packed light brown sugar
- 4 eggs
- 2 teaspoons vanilla extract
- ¼ tsp salt
- 1 cup all-purpose flour
- 1/2 cup walnuts, chopped
- 1/2 cup semi-sweet chocolate chips
- non-stick baking spray
- 1 cup creamy peanut butter
- 1/4 cup salted butter, at room temperature
- 2-3 cups confectioners' sugar
- up to 1/4 cup heavy cream or whole milk
- 1/2 teaspoon vanilla extract
- Preheat oven to 350 F. Line one 12-cup and one 6-cup muffin pan with paper liners.
- Melt chocolate and butter together in top of large double boiler or in large bowl in microwave using the melt chocolate setting; stir until smooth and combined, then cool to lukewarm.
- Whisk in brown sugar until well blended, then eggs one at a time, whisking until completely absorbed before adding the next. Whisk in vanilla extract and salt.
- Toss the nuts and chocolate chips in the flour, add to batter and fold until completely combined.
- Lightly spray the cupcake liners with non-stick spray and use an ice cream scoop to fill dividing batter evenly among each (about 3/4 of the way full). Bake about 25 minutes or until a toothpick in center shows some moist crumbs, and the tops are dry and crackly.
- Cool pans on wire racks for 5-10 minutes, then remove cupcakes to wire racks to cool completely.
- Beat peanut butter and butter together on medium speed until creamy and well combined. Beat in vanilla.
- Add confectioners sugar a cup at a time alternating with a tablespoon of heavy cream until it reaches a spreadable consistency (not too thin or thick, when you lift the beater it shouldn't drip right off). Beat 3-4 minutes longer on medium speed until light and fluffy. Frost cupcakes immediately.