The night before, mix sea salt with sugar, garlic and herbs. Marinate loin for 12 hours at fresh. Once this time is up, remove salt and rinse. Soak in water for 3 hours to desalinate. Confit with duck fat for 3 to 4 hours in the oven at 250°F (120°C) until the temperature reaches 154°F (68°C) on a cooking thermometer. Remove from oven and cool down.
Heat milk. Add polenta, salt, pepper and parsley. Cook for 5 minutes. At the end, add olive oil. Set in a bag and make four rolls. refrigerate for 30 minutes.
Sweat leek with oil. Deglaze with red wine and vinegar. Add brown sugar and mustard. Slowly cook until complete evaporation of the liquids.
Rehydrate morels with warm water then blanch. Sweat with shallot into oil and butter for 3 to 4 minutes. Deglaze sherry. Add brown stock then simmer for 2 to 3 minutes. Set aside.
Slice loin into thick slices. Warm up in the oven.
While the pork loin warms up in the oven, fry polenta nuggets into oil.
Spread loin slices, polenta rolls, mostarda and morels into plates. Coat each portion with sauce.