The classic chocolate chip bar cookie, this is easy to make and very good.
Preheat the oven to 350 degrees F. Grease a 10-inch by 15-inch baking sheet.
In a large mixing bowl, cream together the shortening, white sugar, and ½ cup of the brown sugar. Add the egg yolks, water, and vanilla and blend well. Sift together the flour, baking powder, soda, and salt. Add to the creamed mixture and blend well. Pat onto the baking sheet to form a thin cookie-crust base. Sprinkle on the chocolate chips.
Beat the egg whites until stiff. Fold in the remaining 1 cup brown sugar. Spread on top of the chips.
Bake for 25 to 30 minutes or until a tester inserted in the center comes out clean. Cool completely before cutting into squares.