Preparation

1. Combine salt, 1/3 cup porcini mushrooms, thyme, and pepper in a small bowl.
2. Rub beef with olive oil. Coat roast in porcini mixture.
3. Refrigerate 1 hour.
4. Preheat oven to 225 F.
5. Place 1/3 cup of porcini mushrooms in a small bowl. Add boiling water. Soak mushrooms.
6. Heat 1 tablespoon of olive oil in a skillet over medium-high heat. Brown roast on all sides, about 2 minutes per side.
7. Transfer roast to a rack in a roasting pan. Roast in oven until an instant-read thermometer registers 130 F for medium-rare, about 4 hours.
8. Remove roast, tent with foil.
9. Increase oven temp to 500 F.
10. Strain mushrooms, reserving the liquid and the mushrooms. Set both aside in separate bowls.
11. In a saucepan heat olive oil over medium heat. Add garlic and shallot and sauté 3 minutes.
12. Add drained mushrooms and wine to the pan. Boil 15 minutes. Add mushroom liquid and rosemary and bring to a boil.
13. Reduce mixture to a simmer and simmer until mixture is reduced by half.
14. Strain mixture into a small saucepan. Heat over medium heat. Whisk in butter 1 tablespoon at a time. Keep warm until serving.
15. Remove foil and roast meat until browned and crisp, 5-10 minutes.
16. Transfer roast to a cutting board, tent with foil, and let rest for 15 minutes.
17. Remove foil and cut off ribs in 1 piece, then slice into individual ribs. Carve roast into 1/2-inch slices. Arrange on serving platter. Top with sauce and serve.