• Preheat the oven to 350℉. Grease an 8-inch square baking pan with melted butter or cooking spray. For easier removal of the brownies, also line the pan with parchment paper.
• In a small bowl, whisk flour and cocoa powder to combine. Set aside.
• Add melted butter and brown sugar to the bowl of a stand mixer fitted with a paddle attachment (or use a medium mixing bowl and hand mixer). Beat on medium speed to combine.

  Add egg, additional egg yolk, maple syrup, and vanilla to the bowl, then beat on high for 1 minute.
• With the mixer set to low speed, gradually add flour mixture. Mix just until there are no visible streaks of flour in the batter.
• Pour batter into prepared baking pan and use a silicone spatula to spread batter to the pan’s edges. Bake for 45 minutes, or until you can remove a toothpick from the brownies without the batter sticking to the toothpick.
• Remove from oven and transfer pan of brownies to a wire rack to cool completely.

Make Frosting

• Add chocolate chips to a medium-sized, heat-proof bowl. Set aside.
• Heat heavy cream in a medium saucepan over medium-high heat. When cream is hot and steaming, but not boiling, remove pan from the heat. Pour the cream over the chocolate chips and use a spoon to stir until chocolate ganache is smooth and creamy.
• Spread the ganache over cool brownies and transfer to the fridge to cool for 30 minutes. When the frosting is cool but not completely set, sprinkle mini M&M’s over the top.