Using a pairing knife, cut 6 (1-inch deep by 3/4 inch wide) slits evenly across top of the loin. Place an equal amount of minced garlic in each slit then a small amount of salt and pepper. Follow with a pinch of chopped sage. Season the loin well with salt and pepper. In a large, heavy-bottom Dutch oven, heat olive oil and butter over medium-high heat. Brown pork on all sides. Remove loin from pot and set aside. Sauté onions, celery and garlic cloves, stirring 2-3 minutes. Add mushrooms and continue to sauté 3 minutes longer. Return the pork to pot. Add milk, cream, remaining sage, basil and thyme. Bring to a low boil, reduce to simmer, cover and cook gently for 2 hours, turning pork every 30 minutes. Loin should be fork-tender at this point. Uncover casserole, remove loin and keep warm. Add pimentos and continue to cook cream until sauce-like consistency is achieved. Adjust seasonings if necessary. When ready to serve, slice loin, place decoratively on a serving platter and top with sage cream. NOTE: If cream is boiled too rapidly while cooking the loin, cream may separate, so be careful.