Preheat oven to 350 degrees F. Spray 9x13 inch pan with non-stick spray or line with parchment paper.
In a medium bowl, add the flour, baking soda, baking powder, cornstarch, and salt. Stir to combine. Set aside.
Mix room temperature butter and sugar together with a mixer until light and fluffy. Now, mix in the egg and vanilla and beat until just incorporated.
Slowly add the dry ingredients to the wet ingredients and mix until combined. Add one cup of white chocolate chips to the mixture and stir with a spatula.
Press cookie dough into prepared pan. Bake cookie dough for 17-22 minutes or until edges are slightly browned, and the middle is starting to set. Remove from oven and immediately top with marshmallows. Return to the oven and another 1-2 minutes or until marshmallows become puffy.
Take out of the oven and let sit for 1-2 minutes to cool slightly. Add the M&M and other festive candy as well as the 1/4 cup of white chocolate chips, broken pretzels, and pretty sprinkles.
Let cool completely and then cut into squares. Enjoy!
For these White Chocolate Cookie Bars, Choose whatever candy you like for this recipe.M&Ms, peanut or milk chocolate. Anything with a candy-coated shell. Whatever you and your gang fancies.
Pastel-colored mini marshmallows would also be fun in this recipe.
At first, it will seem like there isn't enough batter to fill the whole pan. Trust us; if you spread it out, it's exactly how much you need :)
Make sure you place the marshmallows on the cookie dough back in the oven for a minute. This way, they’ll melt together and create a delicious pillow for your candy toppings and sprinkles.
Store in an airtight container on the counters for about 5 days.
Nutritional information is approximate and was calculated using a recipe nutrition label generator.★ Did you make this recipe? Don't forget to give it a star rating below!