For the Brownies:
- 1 cup (2 sticks) unsalted butter
- 2 cups granulated sugar
- 4 large eggs
- 1 teaspoon vanilla extract
- 1 cup all-purpose flour
- 1/2 cup unsweetened cocoa powder
- 1/4 teaspoon salt
For the Cosmic Frosting:
- 1 1/2 cups semisweet chocolate chips
- 1 cup sweetened condensed milk
- 2 tablespoons unsalted butter
- 1/2 cup rainbow sprinkles
Preheat your oven to 350°F (175°C). Grease a 9×13 inch baking pan and line it with parchment paper, leaving an overhang on the sides for easy removal later.
In a medium saucepan, melt the butter over low heat. Once melted, add the granulated sugar and stir until well combined. Remove the saucepan from heat and let it cool for a few minutes.
Add the eggs one at a time to the butter-sugar mixture, stirring well after each addition. Stir in the vanilla extract.
In a separate bowl, whisk together the flour, cocoa powder, and salt. Gradually add the dry ingredients to the wet ingredients, stirring until just combined. Be careful not to overmix.
Pour the brownie batter into the prepared baking pan, spreading it evenly. Bake in the preheated oven for 25-30 minutes or until a toothpick inserted into the center comes out with a few moist crumbs. Allow the brownies to cool completely in the pan.
While the brownies are cooling, prepare the cosmic frosting. In a heatproof bowl set over a pot of simmering water (double boiler), melt the chocolate chips, sweetened condensed milk, and butter. Stir continuously until the mixture is smooth and well combined.
Once the brownies are completely cooled, pour the cosmic frosting over the top, spreading it evenly with a spatula. Immediately sprinkle the rainbow sprinkles on top of the frosting.
Allow the cosmic frosting to set for at least 1-2 hours before cutting into squares.
Use the parchment paper overhang to lift the brownies out of the pan. Place them on a cutting board and cut into squares.
Enjoy your homemade cosmic brownies with a burst of chocolatey goodness and colorful sprinkles!
Store the brownies in an airtight container at room temperature for up to a week, or refrigerate for longer freshness.