Preheat the Oven: Preheat your oven to 350°F (175°C). Line an 8×8-inch baking pan with parchment paper, leaving some overhang for easy removal. Lightly grease the parchment paper.

Melt the Butter: In a microwave-safe bowl, melt the butter in the microwave or on the stovetop. Let it cool slightly.

Mix Wet Ingredients: Stir the sugar into the melted butter until well combined. Beat in the eggs one at a time, then mix in the vanilla extract.

Combine Dry Ingredients: In a separate bowl, whisk together the flour, cocoa powder, salt, and baking powder. Gradually add the dry ingredients to the wet mixture, stirring until just combined. Be careful not to overmix.

Fold in Mix-Ins: Gently fold in the chocolate chips and 3/4 cup of the M&Ms into the batter.

Bake the Brownies: Spread the batter evenly into the prepared baking pan. Press the remaining 1/4 cup of M&Ms onto the top of the batter for decoration.

Bake: Bake for 25-30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs (not wet batter). The edges should be set, but the center may still look slightly soft—it will firm up as it cools.

Cool and Slice: Let the brownies cool completely in the pan on a wire rack (about 1-2 hours). Use the parchment paper overhang to lift the brownies out of the pan, then cut into squares.

Serve and Store: Serve as-is or with a scoop of vanilla ice cream for an extra indulgent treat. Store leftovers in an airtight container at room temperature for up to 3 days or in the refrigerator for up to 5 days.