Preheat the oven to 400 degrees F.
Bake the sausage on a baking sheet for 20 minutes. Turn the sausage and bake it 5 to 10 minutes more, until it's fully cooked. Cool to room temperature.
Unfold the puff pastry on a lightly floured board. Cut each piece in half lengthwise and brush the top sides with mustard. Divide the sausage into 4 equal pieces. Starting at the long end of the pastry, place 1 piece of the sausage on top of the mustard and roll it up tightly, overlapping the end by 1/2 inch and sealing the pastry by brushing the edge with water. Cut off the excess pastry. Roll the other 3 pieces of sausage in puff pastry. Place the 4 rolls, seam side down, on a baking sheet lined with parchment paper. Brush with the egg wash. Lightly score each roll diagonally to make 7 equal pieces. Bake for 20 to 25 minutes, until browned. Slice and serve immediately with mustard.
Photograph by Quentin Bacon
The Barefoot Contessa Cookbook (c) 1999 by Ina Garten. By arrangement with Clarkson Potter/Random House, Inc. for Food Network Magazine