In a heatproof bowl, melt the butter and chocolate chips together, stirring until smooth. You can use the microwave method or the double boiler method.
In a separate bowl, whisk together the sugar, eggs, and vanilla extract until light and slightly fluffy.
Gradually add the melted chocolate mixture into the egg mixture.
Sift in the cocoa powder, flour, salt, and baking powder. Gently fold everything together until just combined—don’t overmix!
Pour the batter into the prepared pan and smooth the top. Sprinkle M&M’s and sprinkles on top.
Bake for 20-25 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.
Enjoy