Poach the sausages in 2 frying pans in half white wine and half water for about 10 minutes. Drain on absorbent paper and cool. Using half the pastry at a time, roll out on a lightly floured board into a square or rectangle about ¼ inch thick. Cut into smaller rectangles with a knife or pastry wheel, making each rectangle slightly longer than the sausage. Spread each rectangle with mustard to your taste, place a sausage on it, and roll it up. Place seam side down on a baking sheet. Brush with beaten egg. Bake in a 450-degree oven 10 minutes. Reduce heat to 350 degrees and continue baking 10 more minutes or until the pastry is nicely browned. These rolls are good hot or cold. They can be made in advance, wrapped in moisture proof, vapor proof freezer bags, and baked on the day you plan to use them.