Preheat an oven to 325⁰F.

Prepare a large baking sheet or 2 smaller cookie sheets by lining with parchment paper or spraying with baking spray.

In a large bowl, combine melted butter, sugar, and vanilla and mix until well combined.

Add the egg white and beat until the egg white is incorporated.

Sift in the flour, cocoa powder, and baking soda and mix until no flour is visible.

Pour mixture into prepared baking sheet and spread very thin.

Place brownie brittle into the preheated oven and bake for 15 minutes.

Remove the brownie brittle from the oven and sprinkle the mini M & M’s evenly over the brittle.

Score the brownies for cleaner edges later. This step is optional.

Place the brownie brittle back into the oven and bake for another 8 to 10 minutes or until the bubbling has stopped around the edges.

Remove the brownie brittle from the oven and allow to cool completely.

Once cooled, break the brittle into pieces and store in an airtight container.