Preheat the Oven: Preheat your oven to 350°F (175°C). Line a 9x13-inch baking pan with parchment paper and lightly grease it.
Mix Wet Ingredients: In a large mixing bowl, whisk together melted butter, granulated sugar, and brown sugar until well combined. Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
Combine Dry Ingredients: In a separate bowl, whisk together flour, cocoa powder, salt, and baking powder.
Make the Batter: Gradually add the dry ingredients to the wet ingredients, stirring gently until just combined. Fold in the chocolate chips and half of the crushed candy-coated eggs.
Bake: Pour the batter into the prepared baking pan and spread evenly. Sprinkle the remaining crushed candy eggs and mini marshmallows (if using) on top.
Bake to Perfection: Bake for 30-35 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs. Be careful not to overbake!
Cool & Serve: Allow the brownies to cool in the pan for about 20 minutes before slicing. Serve and enjoy!