Directions

1. Adjust oven rack to middle position and heat oven to 350 degrees. Grease 13x9-inch baking pan. Whisk flour, baking powder, baking soda, and salt in large bowl.
   
2. With electric mixer on medium speed, beat butter, 1 cup brown sugar, and sugar until fluffy. Beat in egg yolks, vanilla, and water. Reduce speed to low and add flour mixture, mixing until combined. Spread dough evenly in prepared pan. Press chocolate chips lightly into dough.
   
3. In clean bowl, whip egg whites to stiff peaks and slowly mix in remaining brown sugar. Spread egg white mixture over dough and bake until golden brown, about 30 minutes. Cool in pan 1 hour. (Bars can be stored in airtight container for 3 days.)