My Easy Bake Cosmic Brownies

Ingredients

• 1 cup (226 g) unsalted butter, melted
• 2 cups (400 g) granulated sugar
• 4 large eggs
• 1 teaspoon vanilla extract
• 1 cup (130 g) all-purpose flour
• 1 cup (90 g) unsweetened cocoa powder
• ½ teaspoon salt
• ½ teaspoon baking powder
• ½ cup (115 g) unsalted butter, softened
• 2 cups (240 g) powdered sugar
• ¼ cup (30 g) unsweetened cocoa powder
• 3 tablespoons milk (more if needed)
• ½ cup (75 g) colorful sprinkles