Ingredients
1/3 cup Dutch-processed cocoa
1 1/2 teaspoons instant espresso (optional)
1/2 cup plus 2 tablespoons boiling water
2 ounces unsweetened chocolate, finely chopped
4 tablespoons (1/2 stick) unsalted butter, melted
1/2 cup plus 2 tablespoons vegetable oil
2 large eggs
2 large egg yolks
2 teaspoons vanilla extract
2 1/2 cups sugar
1 3/4 cups unbleached all-purpose flour
3/4 teaspoon table salt
6 ounces bittersweet chocolate, cut into 1/2-inch pieces
for the filling
4 tablespoons unsalted butter, melted
1/2 cup confectioners’ sugar
3/4 cup smooth peanut butter
1/4 teaspoon salt
1/2 teaspoon pure vanilla extract
Directions
Heat oven to 350F degrees. Make a foil sling for your 13 x 9 inch pan. Spray with nonstick cooking spray.
Whisk cocoa, espresso powder (if using), and boiling water together in large bowl until smooth. Add unsweetened chocolate and whisk until chocolate is melted. Whisk in melted butter and oil. Add eggs, yolks, and vanilla and continue to whisk until smooth and homogeneous. Whisk in sugar until fully incorporated. Add flour and salt and mix with rubber spatula until combined. Fold in bittersweet chocolate pieces.
Next, make the filling: Stir together butter, confectioners’ sugar, peanut butter, salt, and vanilla in a bowl until smooth.
Pour one-third of batter into prepared pan and spread evenly with a spatula. Drop dollops of peanut butter filling (about 1 tablespoon each) on top of batter, spacing about 1 inch apart. Drizzle remaining batter on top, and gently spread to fill pan. Drop dollops of remaining filling on top. Gently swirl peanut butter filling into batter with a butter knife, running the knife lengthwise and crosswise through layers.
Bake until a toothpick inserted into brownies comes out with a few crumbs but is not wet, about 45-50 minutes. Let cool for at least 1 hour in the pan. Using foil overhang, lift brownies from pan. Return brownies to wire rack and let cool completely, about 1 hour more. Cut into 2-inch squares and serve.
