Preheat your oven to 350 degrees fahrenheit.

Spray a 10 inch springform pan, or a 10 inch round cake pan with non-stick spray.

In a large bowl, beat ½ cup of butter until smooth.

Add in brown sugar and sugar, and mix well to combine.

Add eggs and 1 ½ tsp. vanilla and mix again.

In another bowl, whisk together all purpose flour, salt, and baking soda.

Slowly add the dry ingredients to the sugar and butter mixture, mixing until just combined.

Fold in chocolate chips and M&Ms.

Press the cookie dough into the prepared pan evenly.

Bake for 20-25 minutes, until golden brown.

Allow the cookie cake to cool completely.

For the frosting, in a large mixing bowl, beat ½ cup butter, until smooth.

Add in powdered sugar, 1 tsp. Vanilla, and milk. Mix until well combined.

Add the frosting to a piping bag with a 1M star tip.

Pipe frosting around the edge of the cookie cake.