Peanut Butter Cookie Bars

1. Preheat the oven to 350F and grease an 8×8 baking dish. Line the bottom and sides with a sheet of parchment paper and allow it to hang over the edges. This will make it easy to lift out the bars once they’ve baked and cooled.
2. Whisk together the flour, cornstarch, oats, baking soda, and salt and set aside.
3. In a large bowl, mix together the butter and peanut butter until smooth. It’s best to use a hand mixer or a stand mixer fitted with the paddle attachment.
4. Mix in the sugars until combined, followed by the egg and vanilla.
5. Lastly, dump in the dry ingredients and mix to combine. 
6. Press the dough into the baking pan and bake for 25-30 minutes or until the edges are golden brown. 
7. Allow the bars to cool completely, still in the pan, then make the marshmallow meringue topping.

Marshmallow Meringue

1. Add the egg whites and sugar to the bowl of a stand mixer. If you don’t have a stand mixer, make sure to use a heat safe bowl. 
2. Place the bowl over a pot of simmering water (filled about 1/2-1/3 of the way full). Make sure it doesn’t touch the water and don’t let the water come to a boil. Whisk occasionally until the sugar is completely dissolved (about 10 minutes). To test, rub some of the mixture between your fingers. If you still feel sugar granules, keep it over the heat until you can no longer feel those granules. 
3. Transfer the bowl to the stand mixer with the whisk attachment and whip on high speed. As it turns white and opaque, add in the cream of tartar and vanilla. Keep whisking until it’s thick and glossy. To test, dunk the whisk into the bowl and pull it out. When you turn it right side up, the meringue should still stand straight.
4. Spread the meringue onto the cooled cookie bars. Use a kitchen torch to lightly toast the top (if you don’t have one, you can omit this step). 
5. Slice and enjoy!