Precisely remove ten to fourteen leaves of savoy cabbage. Blanch in boiling salted water for three minutes. Remove, spread out on a kitchen towel and dry with kitchen roll. Remove the rough center rib from the bottom of each sheet.
Spread the puff pastry on the surface so that the narrow side is at the bottom. Sprinkle the Gruyère over the bottom half of the pastry. Spread the savoy leaves on top, overlapping just a little longer than the sausage, leaving a margin of in about five cm free.
Sprinkle the leaves with the Sbrinz or Parmesan cheese.
Skin the sausage and coat with mustard. Place it on the savoy leaves. Wrap the sausage leaves at the beginning and then the dough around it. If necessary, cut back the side ends to about three centimeters and fold them over. Place the dough packet, seam side down, on a baking sheet lined with parchment paper. Decorate with scraps of dough as desired. Stir egg yolks and cream together to coat the pie. If possible, let cool for at least fifteen minutes before baking.
Bake the sausage in the dough in the oven heated to 200 degrees for thirty to thirty-five minutes until golden brown.