In a large bowl, cut cold butter or margarine into flour until the mixture has a crumb-like texture. Make a well in the center, add cold water. Mix together until the mixture forms a ball. Do not overmix. Chill dough.
Preheat oven to 450 degrees F (225 degrees C). Grease cookie sheets.
In a medium bowl, blend together almond paste, eggs, 3/4 cup sugar, almond extract and salt.
Divide dough in 4 parts, and roll into 15 inch strips. Place filling along the center of each long strip of dough. Roll up, and pinch the ends to seal. Place strips 2 inches apart on cookie sheet. Brush with egg white, and sprinkle with the remaining sugar.
Bake for 15 to 20 minutes, or until golden.