Food & Cooking Recipes Dessert & Treats Recipes Brownie Recipes Peanut-Butter Swirl Brownies 3.6 (422) 24 Reviews By Martha Stewart Test Kitchen Martha Stewart Test Kitchen The recipes developed by our test kitchen team have undergone a rigorous process of development and testing, ensuring that every element is optimal, from ingredient amounts to method and cooking time. This process includes triple-testing recipes to ensure they meet our high standards. The many stellar cooks and food editors who have been part of our team include Sarah Carey, Lucinda Scala Quinn, Jennifer Aaronson, Shira Bocar, Anna Kovel, Greg Lofts, Riley Wofford, Lauren Tyrell, and Lindsay Leopold. Editorial Guidelines Updated on August 1, 2017 Print Rate It Share Share Tweet Pin Email Photo: Con Poulos Yield: Makes 9 large or 16 small squares Dollops of peanut butter filling are spooned onto brownie batter; pulling a knife back and forth through both results in a marbleized look. Ingredients For the batter 8 tablespoons (1 stick) unsalted butter, cut into small pieces, plus more for pan 2 ounces good-quality unsweetened chocolate, coarsely chopped 4 ounces good-quality semisweet chocolate, coarsely chopped ⅔ cup all-purpose flour ½ teaspoon baking powder ¼ teaspoon salt ¾ cup granulated sugar 3 large eggs 2 teaspoons pure vanilla extract For the filling 4 tablespoons unsalted butter, melted ½ cup confectioners' sugar ¾ cup smooth peanut butter ¼ teaspoon salt ½ teaspoon pure vanilla extract Directions Preheat oven to 325 degrees. Line a buttered 8-inch square baking pan with foil or parchment paper, allowing 2 inches to hang over sides. Butter lining (excluding overhang); set pan aside. Make batter: Put butter and chocolates in a heatproof medium bowl set over a pan of simmering water; stir until melted. Let cool slightly. Whisk together flour, baking powder, and salt in a separate bowl, and set aside. Whisk granulated sugar into chocolate mixture. Add eggs, and whisk until mixture is smooth. Stir in vanilla. Add flour mixture; stir until well incorporated. Make 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 rubber spatula. Place dollops of filling (about 1 tablespoon each) about 1 inch apart on top of batter. Drizzle remaining batter on top, and gently spread to fill pan. Place dollops of remaining filling on top. With a butter knife, gently swirl filling into batter, running knife lengthwise and crosswise through layers. Bake until a cake tester inserted into brownies (avoid center and edges) comes out with a few crumbs but is not wet, about 45 minutes. Let cool slightly in pan, about 15 minutes. Lift out brownies; let cool completely on a wire rack before cutting into squares. Cook's Notes To swirl brownies, work quickly so that batter and filling don't set. Use two large spoons to drop dollops of filling on the first layer of batter about one inch apart. Repeat with next layer of batter and remaining filling. Drag a butter knife back and forth through the layers with the tip touching the bottom of the pan. Rate it Print