Preheat to 350 degrees. Grease a 13" x 9" casserole dish.
In a medium-sized bowl, add the softened butter and sugar and cream together.
Next, add the two egg yolks, one whole egg, and vanilla and mix.
Add the flour, salt, and baking powder and mix until well blended.
Press the cookie dough into the greased pan.
Sprinkle the chocolate chips and mini marshmallows on top.
In a medium-sized bowl, add the two egg whites and beat until stiff peaks form.
Add the brown sugar and mix until blended.
Gently spread on top of the chips and marshmallows.
Bake for approximately 30 minutes. The top will be a golden brown and a cake tester comes out clean.