Chocolate-Peanut Butter Cake | America's Test Kitchen

Ingredients

• 1½ cups (7½ ounces/213 grams) all-purpose flour
• 1 teaspoon baking soda
• ½ teaspoon baking powder
• ¼ teaspoon salt
• 1¼ cups boiling water
• 4 ounces (113 grams) unsweetened chocolate, chopped
• ½ cup (1½ ounces/43 grams) Dutch-processed cocoa powder
• 1 teaspoon instant espresso powder or instant coffee powder
• 10 tablespoons unsalted butter, softened
• 1½ cups packed (10½ ounces/298 grams) light brown sugar
• 3 large eggs, room temperature
• ½ cup sour cream, room temperature
• 1 teaspoon vanilla extract
• 1 cup (7 ounces/198 grams) sugar
• 5 large egg whites
• ⅛ teaspoon salt
• 28 tablespoons (3½ sticks) unsalted butter, cut into 28 pieces and softened
• 1 cup creamy peanut butter
• 1¼ teaspoons vanilla extract
• 4 ounces (113 grams) bittersweet chocolate, chopped
• 4 tablespoons unsalted butter, cut into 4 pieces
• 2 tablespoons light corn syrup
• ½ cup candied peanuts