Creating Monster Mash Brownies is a straightforward process, perfectly suited for bakers of all levels. Follow these steps to bake your deliciously spooky treat:

1. Preheat the Oven: Set your oven to 350°F (175°C) and grease a 9×13 inch baking pan.
2. Mix Wet Ingredients: In a large mixing bowl, combine the melted butter and sugar. Stir until well blended.
3. Add Eggs and Vanilla: Beat in the eggs, one at a time, mixing well after each addition. Then stir in the vanilla extract.
4. Combine Dry Ingredients: In another bowl, whisk together the flour, cocoa powder, baking powder, and salt.
5. Combine Mixture: Gradually add the dry mixture to the wet ingredients, stirring until just combined. Be careful not to overmix.
6. Add Chocolate Chips: Fold in the semi-sweet chocolate chips for that extra indulgent flavor.
7. Pour and Spread: Pour the batter into the prepared baking pan, spreading it evenly to ensure uniform baking.
8. Bake: Place in the preheated oven and bake for 30-35 minutes or until a toothpick inserted into the center comes out clean.
9. Cool: Once baked, remove from the oven and allow the brownies to cool in the pan for about 15-20 minutes, then transfer to a wire rack to cool completely.
10. Decorate: Once cool, use the green, orange, or purple frosting to create fun designs. Add sprinkles and candy eyeballs to complete your Monster Mash look!