Directions

1. Preheat oven to 450 degrees F (230 degrees C). Rinse the roast, and pat dry with paper towels. Sprinkle black pepper and rosemary over the top and sides of the meat, and set aside.
2. In a large bowl, mix the rock salt with the flour, and slowly work in 3/4 cup of cold water or as needed, about 1 tablespoon at a time, to make a sticky paste. Place a 1/2-inch thick layer of the rock salt paste into the bottom of a roasting pan. Lay the meat, ribs down, onto the paste. Lay the bacon strips over the top of the roast. Smear rock salt paste liberally all over the roast, coating the top, sides, and bottom of the meat. Reserve about 1/4 cup of the paste.
3. Bake the roast in the preheated oven until seared and brown, 20 to 30 minutes. Remove the roast from the oven, and check for holes in the paste coating; repair with reserved paste. Reduce oven temperature to 325 degrees F (165 degrees C). Return the roast to the oven, and cook until browned and an instant-read meat thermometer inserted into the thickest part of the meat, not touching bone, reads 130 degrees F (54 degrees C) for medium-rare, about 1 more hour. Remove the roast, and allow to stand for about 30 minutes. Temperature will rise to 140 to 145 degrees F (60 to 65 degrees C) as it rests.
4. Melt butter in a large skillet over medium heat, and cook and stir the mushrooms until browned and their liquid has almost evaporated, about 15 minutes. Stir in 6 cups of cold water, and whisk in the au jus gravy mix until smooth. Stir in the red wine. Bring the sauce to a boil, reduce heat, and simmer, stirring constantly, until the sauce has thickened.
5. To serve, break off and discard the salt crust from the meat; slice, and serve with mushroom gravy.