MUSHROOM SAUCE FOR BEEF TENDERLOIN ROAST RECIPES

Steps:

• Preheat the oven to 400 degrees F.
• Heat a large ovenproof skillet over medium-high heat. Pat the beef dry and season all over with salt and a generous amount of pepper. Add the oil to the skillet and heat until shimmering. Add 1 tablespoon of the butter and swirl to melt. Add the beef and sear until mahogany brown on all sides, about 8 minutes total.
• Transfer the skillet to the oven. Roast until an instant-read thermometer inserted in the center registers 125 degrees F for medium rare, about 25 minutes. 
• Meanwhile make the ragout: Heat 2 tablespoons of the butter in a large skillet over medium-high heat. Add the mushrooms and spread them out evenly; increase the heat to high. Let the mushrooms cook, undisturbed, until browned, then shake the skillet to flip them over. Add the additional butter along the sides of the skillet as the mushrooms cook if the skillet seems very dry. Continue to cook until nicely browned, about 5 minutes. 
• Add the shallot and cook, stirring often, until softened, about 2 minutes. Season the mushrooms with 1/2 teaspoon salt and some pepper; add the thyme. Pull the skillet off the heat and add the Madeira. Return the skillet to the heat and scrape up any of the brown bits from the bottom with a wooden spoon. Add the heavy cream and bring to a boil. Remove from the heat and keep warm.
• When the beef is ready, transfer to a cutting board, tent very loosely with aluminum foil and let rest for 10 to 15 minutes.
• Slice the beef across the grain, arrange on a platter and serve with the mushroom ragout.

Steps:

• Remove the tenderloin from the refrigerator 1 hour prior to cooking.
• On the tail end of the tenderloin, about a third of the way from where it begins to taper, make an incision almost all the way through the beef. Fold the tail onto the larger portion to make an even cylinder throughout. Use ten to twelve 8-inch pieces of butcher's twine to tie the tenderloin crosswise every 3/4 to 1 inch. This will help it to keep its shape and cook evenly.
• Preheat the oven to 225 degrees F.
• Pat the tenderloin dry. Brush with 1 tablespoon of the olive oil and season heavily with salt and pepper all around. Put the remaining 3 tablespoons olive oil in a cast-iron pan over medium-high heat. When hot, add the beef and sear on all sides until a nice crust is formed, 1 to 2 minutes per side. Add the thyme, garlic and 3 tablespoons of the butter to the pan. Once the butter is melted, use a spoon to baste the beef with the herb and garlic infused butter for 30 seconds.
• Transfer the beef to a rack on a baking sheet, spoon over 2 tablespoons of the herb and garlic butter mixture from the cast-iron pan (reserve the pan) and roast until the internal temperature of the thickest part reaches 120 degrees F (for medium rare), 1 to 2 hours, depending on the size of the tenderloin. Cover the beef with foil and rest for 15 minutes.
• Add the shallots to the remaining herb and garlic butter mixture in the cast-iron pan and sweat over medium heat until translucent, 3 to 5 minutes. Deglaze with the red wine and reduce until almost dry, 5 to 8 minutes. Add the beef stock, bring to a simmer and reduce by half, 10 to 15 minutes.
• Meanwhile, thoroughly mix the remaining 2 tablespoons butter with the flour in a small bowl.
• Reduce the heat to low and slowly whisk in the butter and flour mixture bit by bit, until the sauce reaches the desired consistency. Serve with the perfectly roasted beef.