Monster Mash Brownies You Can Actually Make on a Busy Weeknight

Name: Monster Mash Brownies You Can Actually Make on a Busy Weeknight
Cuisine: American
Ingredients: 1 cup (225g) butter, melted; 2 cups sugar; 4 eggs; 1 tablespoon vanilla extract; 1 cup all-purpose flour; ¾ cup unsweetened cocoa powder; ½ teaspoon salt; ½ teaspoon baking powder; For the monsters; ½ cup softened butter; 2 cups powdered sugar; 1 to 2 tablespoons milk; 1 teaspoon vanilla; Gel food coloring in green, purple and orange