Step 1: Prepare the Fudgy Brownies

1. Preheat Oven: Preheat your oven to 350°F (175°C). Grease a 9×9-inch baking pan or line it with parchment paper for easy removal.
2. Melt Butter: In a medium saucepan over low heat, melt the butter. Remove from heat and stir in the granulated sugar, eggs, and vanilla extract until well combined.
3. Add Dry Ingredients: Stir in the cocoa powder, flour, salt, and baking powder until just combined. If using, fold in the chocolate chips.
4. Spread in Pan: Pour the brownie batter into the prepared baking pan and spread it evenly.

Step 2: Prepare the Monster Cookie Layer

1. Mix Wet Ingredients: In a large mixing bowl, beat together the softened butter, peanut butter, brown sugar, and granulated sugar until creamy. Add the egg and vanilla extract, mixing until smooth.
2. Add Dry Ingredients: Stir in the rolled oats, flour, baking soda, and salt until just combined. Fold in the chocolate chips and M&M candies.
3. Spread on Brownies: Carefully dollop the monster cookie mixture over the brownie layer. Use a spatula to gently spread it out evenly.

Step 3: Bake

1. Bake: Bake in the preheated oven for 30-35 minutes, or until the edges are set and a toothpick inserted in the center comes out with a few moist crumbs (it’s okay if it’s slightly underbaked for a fudgy texture).
2. Cool: Allow the brownies to cool in the pan for about 15-20 minutes before slicing into squares.

Step 4: Serve

1. Enjoy: Serve your Monster Cookie Fudgy Brownies warm or at room temperature. They can be stored in an airtight container for up to a week.