Saute the reconstituted morel mushrooms in 2 tablespoons of butter until tender, about five minutes. Mix the mushrooms with the cooked wild rice.
Preheat the oven to 350 degrees F.
Use a long slender knife to carve a small tunnel horizontally through the center of each tenderloin. Chop the carved out meat and reserve. Use the handle of a wooden spoon to firmly pack the rice and mushroom mixture into the tunnels in the tenderloins.
Place the stuffed tenderloins on a rack in a roasting pan and rub with 1 tablespoon of oil. Sprinkle with 1 teaspoon of marjoram, salt, and pepper.
Scatter the onion, carrots, garlic, and chopped meat around the rack in the pan. Drizzle with about 1 tablespoon of oil and sprinkle with another teaspoon of marjoram.
Roast for about 1 1/2 hours, or until the meat is no longer pink and the vegetables are tender.
Transfer the pork to a cutting board and cover with foil to keep warm.
Whisk the butter, flour, and mustard in a small bowl to blend thoroughly.
Add the broth and wine to the roasting pan. Place the pan over two stove top burners and simmer the juices over medium heat until the mixture is reduced to about 1 1/2 cups, scraping up the browned bits.
Strain the liquid into a small saucepan and skim the fat from the surface. Bring to a boil and whisk in the mustard mixture. Simmer until the sauce thickens, whisking frequently.
Season with salt and pepper.