1. Preheat a conventional oven to 350°F.
2. In a large mixing bowl, cream together the butter and ½ cup of sugar. Add the egg and the egg yolk one at a time until incorporated well.
3. In a separate bowl, sift together the flour, sugar, cocoa and salt.
4. Add the sifted ingredients to the creamed mixture a little bit at a time until all the dry ingredients are mixed in well.
5. Spread the mixture out into a sheet pan about ½ inch thick. Place in preheated oven and blind bake approximately 10 minutes.