Preheat the oven to 350 degrees Fahrenheit.
Prepare the sugar cookie mix according to the package directions using a stand mixer. Press into the bottom of a greased 9x13 pan.
Wipe clean the stand mixer bowl and paddle attachment and then prepare the brownie mix according to package directions. Add in the mint extract while mixing. Pour the brownie mix on top of the sugar cookie dough. Smooth with a spatula and then add in the semi-sweet chocolate chips.
Bake at 350 degrees for 35-40 minutes. Let cool for at least 1 hour. Cut around the edges to loosen the brownies and flip over on to a large plate or cutting board, then flip again so that the brownies are facing upwards.
Cut each brownie into equal squares.
Melt white chocolate in microwave according to package (or over a double-boiler on the stove-top). Drizzle white chocolate over cook bars. Top with M&M's® White Chocolate Peppermint Candies and holiday sprinkles. Let the white chocolate set for at least a half hour, package in GLAD® containers, and enjoy!