Dutch Shortbread Boterkoek 1973 - cooking recipe

Ingredients

1 cup unsalted butter
1 cup solid-type firm margarine
1 cup granulated sugar
3 cups all-purpose flour
1 dash salt, helps bring out flavours (optional)
1 egg, separated
1 teaspoon vanilla
1 tablespoon cold milk

Preparation

Cream the room temperature but not too soft butter and margarine together with the sugar using a wooden spoon.
Add the vanilla and unbeaten egg white only.
Add the flour until a stiff dough forms, and can be handled.
With floured hands pat into an 10 x 16 baking pan about 3/4 of an inch thick.
Beat the egg yolk with the milk until combined well making an egg wash and brush over the patted out dough.
Bake in an 300 degree, preheated oven for about 25 minutes or until slightly golden in colour.
When still slightly warm, then score into squares or triangles. Cool thoroughly before storing into cookie tins.