Bring a boneless pork loin to room temperature. (Any size will do but you will need to watch the cooking time for smaller roasts. A 3 pound roast will take about an hour in the oven).
Pour 2 cups boiling water over about two cups of mushrooms (dried Porcini, Crimini, whatever you like) and let stand for 30 minutes. (I used Crimini's that I had left over and which had dried out slightly and this worked perfectly). Remove mushrooms and reserve mushroom water by pouring through a coffee filter or fine sieve.
Stuffing:
1/2 cup shallots or yellow onions, chopped
3 - 4 cloves garlic, minced
3/4 cup fine bread crumbs
1/4 cup chopped parsley leaves
2/3 of soaked mushrooms, minced
Salt and pepper to taste
Saute onion and garlic over medium high heat until softened.
Transfer to a bowl and add remaining ingredients.
Let cool.
With a long thin knife cut a slit through the center of the pork loin (about an inch to an inch and a half wide) and stuff it with the mushroom stuffing. You can push it through with a wooden spoon or just keep pushing it in with your fingers.
Season outside of pork loin with salt and pepper.
Heat 1/2 Tbsp oil over high heat in a cast iron skillet until it just starts to smoke, then brown loin on all sides (about 1 1/2 minutes total).
Transfer skillet and loin to 375º oven. Roast for about an hour or until internal temperature reaches 155º.
Rest for ten minutes, slice and serve.
Gravy:
Deglaze hot frying pan with juice of two limes. Add two cups of stock, reserved mushroom liquid, and remaining mushrooms (chopped). Simmer, stirring occasionally, for about five minutes.
