Ingredients
Method
- Whisk together the flour, cornstarch, baking soda, baking powder, and salt for the cookie layer until evenly combined.
- Beat the softened butter with the brown sugar and granulated sugar until pale and fluffy, then blend in the peanut butter until smooth.
- Mix in the vanilla extract and egg until fully incorporated, scraping the bowl once if needed.
- Fold the dry ingredients into the wet mixture just until combined, then stir in the oats, mini chocolate chips, and mini M&M's. Cover and refrigerate for 40 minutes.
- Near the end of the chilling time, preheat the oven to 325°F and line a 9×9-inch baking pan with parchment paper before lightly greasing it.
- Whisk together the flour, cocoa powder, cornstarch, and salt for the brownie batter in a separate bowl.
- Beat the sugar, eggs, and egg yolk for about 5 minutes until thick, pale, and fluffy while allowing the melted butter to cool slightly.
- Blend the melted butter, oil, and vanilla into the whipped egg mixture on low speed until smooth.
- Gently fold the dry ingredients into the wet mixture with a spatula, then fold in both kinds of chocolate chips without overmixing.
- Spread the brownie batter evenly into the prepared pan and smooth the surface.
- Bake the brownie layer for 15 minutes until the surface is lightly set but the center remains soft.
- Flatten small portions of the chilled cookie dough into discs and arrange them across the partially baked brownies until the surface is covered.
- Return the pan to the oven and bake for 20 minutes. Loosely tent the pan with foil and continue baking for another 5–10 minutes until both layers are fully set with no noticeable jiggle.
- Cool the bars completely in the pan on a wire rack before lifting them out and slicing into 16 squares.
Nutrition
Notes
Every bite delivers gooey brownie richness with chewy peanut butter cookie goodness on top. These bars slice beautifully once cooled and are perfect for sharing with family or friends.