Roasting chateaubriand involves mixing the ingredients and roasting until the meat is the desired level of doneness. Chateaubriand is a steak made from a center-cut fillet.
Before starting to cook the chateaubriand, allow it to sit at room temperature for 15 minutes. Season the meat with salt and pepper. Heat 3 tablespoons olive oil in an oven-safe skillet over high heat. Place the meat in the pan and sear on all sides until it's browned.
Reduce the heat to low, and add 2 tablespoons unsalted butter cut into pieces. Mix in 1 1/2 cups quartered mushrooms, 4 smashed garlic cloves and 4 sprigs fresh thyme. Roast in an oven preheated to 350 F until it reaches the desired level of doneness. After roughly six to eight minutes, the internal temperature should be 125 to 130 F, which is rare.
To make a wine reduction sauce for the chateaubriand, transfer the roasted meat to a cutting board, and create a foil tent over the top. Place the cooked mushrooms in a bowl, discard the garlic and thyme, and pour off all but 1 tablespoon of the fat. Add minced shallots and 1/2 cup red wine, scraping off the browned bits.
Cook until the wine is mostly evaporated, and then add 2 cups beef broth and 1/4 cup heavy cream. Cook five minutes or until the sauce thick. Add the mushrooms, and serve over the chateaubriand.