Heat a large Dutch oven over medium-high heat. Add the olive oil and saute the garlic, rosemary and sage for a couple of minutes. Add the pork loin to the pan, gently sliding it on top of the herbs to prevent the hot oil from jumping onto your skin.
Saute the pork for about 5 minutes on each side, then remove it from the pan and set aside on a plate. Add the wine to the pan and use a wooden spoon to scrape the bottom of the pan; cook until the smell of the alcohol has disappeared, 1 to 2 minutes.
Lower the flame to a very low-medium heat. Return the pork to the pan and season with salt and pepper. Partially cover with a lid and cook for about 1 1/2 hours, flipping the pork and scraping the bottom of the pan every 15 to 20 minutes. Keep an eye on the sauce, making sure it does not reduce too much; add some warm water if necessary, always in very small increments.
When the pork is ready, remove the pan from the heat and let cool for about 30 minutes. Remove the pork to a cutting board.
When the sauce is cooled, add the milk and put the pan back on the stove. Heat gently over medium-low heat, stirring the sauce constantly. This will prevent any curd from forming and will produce a wonderful and soft creamy sauce. Slice the pork and serve with the sauce.