In a medium bowl, combine granulated sugar, brown sugar and shortening. Beat until well combined.
Add 2 egg yolks, vanilla and 2 tsp. of water to above mixture. Combine well.
In a separate bowl, combine flour, baking powder, baking soda, baking powder, and salt.
Add dry mix to wet until combined. Dough will appear crumbly.
Press the dough evenly onto the greased baking pan. Dough will be about 1/2" thick.
Pour 1 package of chocolate chips over the dough. Set aside to make topping.