Crisp shin of lamb with salted zabaione and Cipolline baby onions

For 6 people

 Spread a thin layer of mustard all over the meat. Roll the onto the puffy paste and seal it. Brush the beaten egg onto the pastry. Bake 180° for 20 minutes. Heat the Cipolline baby onions in a small saucepan. Take a metal bowl and place over a bain-marie. Add the egg yolks and beat well with a whisk. Add the the Parmigiano Reggiano cheese and the fresh cream. Continue gently heating and stir until creamy.  Add the mixture in the dishes. Add the sliced lamb on top. Serve with Cipolline baby onions in balsamic vinegar.