Six different types of peppercorns give the rich cognac-based sauce a kick in this decadent beef tenderloin recipe.
Bring 2 cups of water to a boil in a small pot. Add raisins, reduce heat, and simmer for 5 minutes. Drain, and rinse raisins under cold running water, and drain again. Place raisins in a small bowl, and pour cognac over. Cover with plastic wrap, and refrigerate overnight.
Season beef with salt, and press peppercorns into the beef to adhere. In a large skillet, heat oil over medium heat. Add beef to skillet, and cook for 4 to 5 minutes on each side for medium-rare. Transfer to a platter, and keep warm.
Drain off the fat from the skillet. Add the raisins and cognac, and place over high heat, and bring to a boil. Cook until the liquid has reduced by half. Add the beef stock, reduce the heat to a simmer, and cook for 2 minutes. Cut the remaining 2 tablespoons butter into very small pieces. While whisking constantly, gradually add the butter to the sauce in the skillet. Continue to whisk until incorporated. Season with salt.
Return the beef to the skillet, and baste with the sauce. Serve the beef and sauce with potatoes and spinach.