Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking pan.

In a large mixing bowl, melt the butter in the microwave or on the stovetop.

Stir in the granulated sugar until well combined.

Add the eggs one at a time, mixing well after each addition, then stir in the vanilla extract.

In a separate bowl, whisk together the flour, cocoa powder, salt, and baking powder.

Gradually add the dry ingredients to the wet mixture, stirring until just combined.

Pour half of the brownie batter into the prepared baking pan and spread it evenly.

In a medium bowl, combine the mini marshmallows, crispy rice cereal, and white chocolate chips.

Spread this mixture over the brownie layer in the pan.

Pour the remaining brownie batter on top, spreading it gently to cover the marshmallow mixture.

Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.

Remove from the oven and let cool in the pan for at least 30 minutes.

Once cooled, sprinkle with red and blue sprinkles for a festive touch.

Cut into squares and serve.