1. The day before, rub the pork loin with salt mixed with white pepper. Place in a shallow dish; cover with milk and 3 sprigs of rosemary. Let it rest in the refrigerator all night.

2. On the same day, pat the pork loin dry and brown it in a Dutch oven with extra virgin olive oil. Drain, discard the cooking fat, and wipe the Dutch oven clean.

3. Put the pork loin back in the Dutch oven; add the milk from the marinade. Surround the meat with chopped onions, crushed garlic cloves, and pepper.

4. Cover the Dutch oven and simmer for 90 minutes over low heat. Turn the pork loin occasionally. Halfway through cooking, add the white wine and drained mushrooms.

5. Remove the pork loin from the Dutch oven. Recover the mushrooms, onions, and rosemary sprigs with a slotted spoon. Place on a plate and keep warm.

6. Emulsify the sauce with an immersion blender. Strain and bring to a simmer. Incorporate the cornstarch diluted in a tablespoon of water, stirring constantly. Adjust the seasoning with salt, pepper, and rosemary.

7. Serve the sliced pork loin with mushrooms on warm plates and drizzled with some sauce. Serve immediately.