In a small bowl combine egg, water, and mustard; set aside. In a medium bowl stir together cheese, onion, parsley, caraway seed, and garlic salt. Unfold pastry sheet. Brush generously with the egg mixture. Sprinkle cheese mixture lengthwise over half of the rectangle. Fold plain half over cheese, lining up edges and pressing to seal. Brush top of pastry with egg mixture. With a sharp knife, cut pastry crosswise into 1/2-inch-wide strips. Twist each strip several times and place 1 inch apart on a greased or parchment-lined baking sheet, pressing ends down. Bake in a 350 degree F. oven for 18 to 20 minutes or until light brown. Serve warm. Makes about 18 appetizers.