Preheat oven to 350.

Combine flour, sugar and salt.

With a pastry blender or a fork, cut in the margarine until the mixture looks like coarse crumbs.
Beat egg in a small bowl.

Stir in milk and peanut butter.

Add egg mixture to flour mixture; stir.

Stir in the water, 1 teaspoon at a time, until the dough forms a ball.
Knead dough for 3 minutes on a lightly floured surface .

Roll dough out to a 1/2-inch-thick rectangle.

Cut into desired shapes with a cookie cutter.

Brush with beaten egg whites, sprinkle with sesame seeds.
Bake about 30 minutes until firm and golden brown.