Remove 1/2 cup of the flour-sugar mixture for rolling out the dough later in the recipe.
To the remaining flour-sugar mixture, work in the butter, cream cheese and egg. Knead it altogether.
With your hands, pat into a ball and wrap tightly with plastic wrap.
Let the dough stand in the refrigerator overnight.
About a half hour before you're ready to start making the cookies, put the dough into the freezer. This will make it easier to work with.
For the filling, mix together the ground walnuts, beaten egg white, honey, almond extract and vanilla extract. Set aside.
Spread the reserved flour-sugar mixture onto the surface where you will be rolling the dough.
Roll the dough out thin.
Cut into squares about 2 x 2 inches. It's easier to cut if you use a pizza cutter.
Place a small amount of filling, about 1/2 teaspoon to 1 teaspoon, into the center of the dough. Be sure not to fill them too much, or the filling will spill out when it is baking.
Fold the corners into the center, partially covering the filling.
Bake in a preheated 375°F oven for about 13 minutes, until golden brown.