Duck breast with walnuts and pan-seared parsley mushrooms

Degrease slightly and remove the nerves while parrying the duck breast. Sauté the breasts on the skin side and then the meat side over low heat (10 to 15 minutes) and set aside. Keep them bloody.
Make a crust of very soft butter, bread crumbs, bread and chopped walnuts. Spread it between two sheets of greasproof  paper (0.8 cm thick). Freeze for a few minutes to harden. Cut the walnut crust into the size of the breasts and place it on the breasts. Grill in the oven to color the crust and finish, if necessary, the cooking of the duck breasts.
Cut the mushrooms into small cubes, add the chopped parsley and chopped garlic. Sauté in butter and perfume with walnut oil.
Peel the potatoes, cut them finely (chips), place them in a rosette on parchment paper, brush them with the fat of the melted breast.
Put in the oven at 150 ° C, 15 minutes until coloring.
Reduce the balsamic vinegar to at least 2/3 then incorporate butter.
Place on a plate the duck breast, accompanied by pan-fried ceps and rosettes of potatoes.
Add a bit of sweet and sour sauce to the plate.