Assemble ingredients and tools. Preheat oven to 375 degrees F.
Chop the carrots and celery. Peel the onions and cut into quarters. Chop the garlic. Cut the peppers into bite-sized pieces. Set aside.
In a shallow dish, combine flour, salt and pepper. Dredge pork in flour mixture, shaking off excess. In a Dutch oven on top of the stove, heat the olive oil and brown the meat on all sides. Transfer the meat to a plate and set aside.
Add the garlic, vegetables and 2 tablespoons stock to the pot, cooking until lightly browned. Stir in the wine and cook until reduced by half, about 2 minutes. Add the remaining stock, bay leaf and thyme and pork tenderloin. Bring to a simmer. Cover the pot and transfer to the oven.
Bake in the oven for about 15 to 20 minutes, until the tenderloin reaches at least 150 degrees internally. Remove the tenderloin and return the pot to the stove. Bring to a simmer and reduce the sauce. If desired, add the cooked mushrooms. Remove the bay leaf, slice the tenderloin into 12 pieces and place on a platter. Cover with sauce and sprinkle with gremolata.
1 Tbsp. chopped fresh parsley
1 Tbsp. freshly grated lemon zest
2 cloves garlic, minced
Sea salt and fresh pepper
In a small bowl, combine parsley, lemon zest and garlic. Season with salt and pepper. Serve within the hour. Leftovers may be used in cooking stocks and soups.