Ingredients

• 1/2 cup smooth peanut butter
• 1/2 cup (1 stick) unsalted butter, at room temperature
• 1 1/2 cups sugar
• 3 eggs
• 1 teaspoon vanilla
• 1 cup flour
• 1 cup peanut butter and/or milk chocolate chips
• 1/4 cup unsweetened cocoa powder

Instructions

1. Preheat the oven to 350 degrees F. Lightly grease or spray a 9-by-13-inch pan.
2. Beat the peanut butter and butter together with a wooden spoon until well blended. Beat in the sugar, then the eggs, one a time. Beat in the vanilla, then the flour just until incorporated.
3. Scrape about half of the batter into the pan and smooth evenly over the bottom. Scatter the chips evenly over the batter.
4. Stir the cocoa powder into the remaining batter. Spoon into the pan, spreading evenly over the chips and peanut butter layer.
5. Bake for 25 to 30 minutes, or until a toothpick inserted into the center comes out mostly clean.
6. Let cool in the pan, then cut into bars.