Beef loin with ribs and stuffing

Ingredients:

• 1 beef loin on 4 bones (about 4.5 kg)
• 30 g dried porcini mushrooms
• 145 g unsalted butter
• 450 g of champignons, finely chopped
• 2 large shallots, finely chopped
• 1 tsp thyme leaves, chopped
• 4 cloves garlic, finely chopped
• 450 g small spinach
• 170 g brioche, cut into 1 cm cubes.
• 2 tbsp black truffle butter, optional

Preparation:

1. Place the porcini mushrooms in a heatproof bowl and pour boiling water over them. Let them sit for about 20 minutes to plump up. Remove the mushrooms with a slotted spoon, allowing the sediment to settle at the bottom of the bowl; finely chop the mushrooms.
2. In a large skillet over medium heat, melt 4 tablespoons butter; add the mushrooms and porcini mushrooms. Cook, stirring occasionally, until all the liquid has evaporated and the mushrooms begin to brown around the edges, about 10 minutes. Add the shallots, thyme, 1/2 teaspoon salt, and a few freshly ground black pepper and cook until the onions are soft and the mushrooms are golden brown, about 5 minutes. Transfer to a baking sheet and spread out in a thin layer to cool to room temperature.
3. Meanwhile, in the same skillet, melt another 2 tablespoons of butter over medium-high heat. Add the garlic and cook, stirring constantly, until fragrant and softened, about 1 minute. Add the spinach and cook, stirring frequently, until tender, about 4 minutes. Sprinkle with 1/2 teaspoon of salt and toss. Transfer the spinach to a colander set over a bowl to drain. Cool to room temperature.
4. While the spinach is cooling, melt the remaining 4 tablespoons butter in a skillet over medium-high heat. Add the brioche cubes and cook, stirring frequently, until golden brown, about 10 minutes. Remove from heat and let cool to room temperature.
5. Preheat oven to 230°C.
6. Using a sharp knife, trim the meat and fat from the rib bones, removing about 4 cm of fat. Trim off any excess fat from the meat so that it is no more than 0.5 cm thick. You can also ask the butcher to trim your ribs for you..
7. Place the meat on a large cutting board, bone-side up. Holding a large, sharp knife parallel to the bones and about 1 inch from the back of the bones, cut straight down until you're about 1 inch from the bottom of the cut. Gently push the meat away from the bone so the bones are standing upright and the meat is resting on the cutting board. Position the knife so it's parallel to the cutting board, and starting where you left off with your last cut, continue cutting the meat about 1 inch up from the board, slowly turning it as you go. You'll have a long, rectangular piece of meat attached to the bone, about 1 inch thick.
8. Once you have an even layer of meat, sprinkle it with 1 tablespoon of salt and 1 teaspoon of black pepper. Spread the mushroom mixture evenly over the meat. Top with brioche cubes, followed by a layer of spinach. Arrange pieces of truffle butter, if using. Starting with the boneless side, roll the meat and filling into a tight roll and tie with twine (tie it along the entire length of the loin between each rib). Sprinkle the outside with 1 tablespoon of salt and 1 teaspoon of black pepper.
9. Place the roast bone-side down on a rack set in a roasting pan and transfer to the oven. Roast for 20 minutes, then reduce the temperature to 350°F (175°C) and continue roasting until the internal temperature reaches 125°F (52°C), about 2.5 hours.
10. Transfer the roast to a cutting board and let rest for 30 minutes before slicing and serving.