While these little goodies are labeled "cupcakes", I think of them as more of a brownie.
Either way, they combine two of my favorite sweet flavors together for one deliciously rich hand held treat.
from Martha Stewart's Cupcakes
2/3 cup flour
1/2 tsp baking powder
1/4 tsp salt
1/2 cup (1 stick) unsalted butter, cut into small pieces
4 ounces semisweet chocolate, coarsely chopped
2 ounces unsweetened chocolate, coarsely chopped
3/4 cup granulated sugar
3 large eggs
2 tsp vanilla
Peanut Butter Filling
4 T (1/2 stick) unsalted butter, melted
1/2 cup confectioners' sugar, sifted
3/4 cup smooth peanut butter
1/4 tsp salt
1/2 tsp vanilla
Preheat oven to 325 degrees F. Line a standard muffin tin with paper liners. Whisk together flour, baking powder and salt. Put butter and chocolates in a heatproof bowl set over (not in) a pan of simmering water; stir until melted. Remove from heat, and let cool slightly.
Whisk granulated sugar into cooled chocolate mixture. Add eggs, and whisk until mixture is smooth. Stir in vanilla. Add flour mixture; stir until well incorporated.
Make Peanut Butter filling by combining butter, confectioners' sugar, peanut butter, salt and vanilla. Stir until smooth.
Spoon 2 tablespoons chocolate batter into each lined cup, followed by 1 tablespoon peanut butter filling. Repeat with another tablespoon of batter and top with 1 teaspoon filling. Swirl top of cupcake batter and filling with a wooden skewer or toothpick.
Bake, rotating tin halfway through, until a cake tester inserted in centers comes out with only a few moist crumbs attached, about 40 minutes. Transfer tin to a wire rack to cool completely before removing cupcakes. Cupcakes can be stored up to 3 days at room temperature in airtight containers.