In the bowl of a stand mixer fitted with paddle attachment, cream the sugars and butter until fluffy. Add the egg yolk mixture and vanilla extract and mix until just combined.
Sift the dry ingredients 3 times and add to the creamed mixture. Mix on medium speed until dough is stiff.
Spread on a greased 10x14-inch baking sheet.
Combine the chips in a small bowl. Sprinkle them evenly over the top of the dough.
For the topping, make sure the mixing bowl is clean and free of any greasy residue or water.
With the whisk attachment, beat the egg whites until stiff, but not dry. Add the brown sugar and vanilla. Beat well. Mixture should be fluffy and form soft peaks.
Spread the mixture over the chips and add any decorative swirl or design that you like.
Bake for 25-30 minutes. Allow to cool. Cut into squares.