Preheat the oven to 325 degrees F. LIne an 8-inch square pan with foil, then butter or oil it and dust with flour.

Mix the chopped dates, walnuts, sugar, flour and baking powder together.

Lightly beat the egg yolks, add them, and mix again. 

Beat the egg whites just a bit (with a fork or whisk), until they begin to foam. Then add them to the rest of the ingredients, mix with your hands, and press the stiff dough into the pan. Even the mixture out, covering the entire bottom of the pan. If you have to, don't be hesitant to move chunks of the "dough" with your hands to achieve a uniform thickness. 

Bake for approximately 20 minutes until the top is lightly browned. Cool the bars in the pan until you can easily move a butter knife around the sides. 

I found it easier to tip the entire pan over onto a cutting board, then peel back the foil before cutting it into squares. You can do that or cut it in the pan and remove them one square at a time.