Preheat oven to 350°F. Line a 9x13 inch pan with foil and spray with nonstick cooking spray.

Melt butter and baking chocolate in a large bowl. Heat on high power for 1 minute then stir, heating in additional 30-second increments until melted and smooth.

Stir in sugar, eggs, vanilla, salt, and cocoa until combined. Stir in flour.

Pour brownie batter into the prepared baking pan. Sprinkle with sprinkles and M&Ms. Bake for 25-35 minutes until a toothpick inserted in the center comes out with a few moist crumbs. Cool before slicing into bars.