1Mash the butter into the flour in a mixing bowl with a pastry cutter or forks until it resembles small peas. Gradually add ice-cold water into the mixture, stirring lightly until the mixture is moist enough to form a ball. Place the pastry ball into a bowl and cover with plastic wrap. Mix almond paste, sugar, eggs, and almond extract in a separate bowl. Cover bowl with plastic wrap. Refrigerate both mixtures 8 hours to overnight.
2Preheat oven to 400 degrees F (200 degrees C). Grease 2 baking sheets.
3Divide the pastry into 10 portions. Using a rolling pin, roll each portion into long strips measuring about 4x12 inches. Divide the almond paste mixture into 10 portions; use your hands to form each portion into a snake shape. Place each almond 'snake' into the center of each pastry strip. Fold the dough over and seal the seam, also closing the ends. A little water will help to hold the seal. Arrange the rolls seam side down onto the baking sheets. Cut slits into the rolls with scissors every 2 inches.
4Beat egg white and water together in a small bowl; brush over the pastry rolls to coat.
5Bake in preheated oven until lightly browned, 20 to 25 minutes. Set aside to cool completely before slicing.
To make the dough, you can use a pastry blender, food processor, or the dough hook on your mixer. It is important to not handle the dough too much because it will cause the dough to become tough.