When it comes to beef, tenderloin is one of the priciest cuts. Our recipe for Slow-Roasted Beef Tenderloin calls for a tenderloin roast that's been trimmed of its silverskin and "chain," or side muscle. If you want to purchase the roast completely trimmed and don't mind paying top dollar for it, just ask your butcher to prepare the roast "side muscle off and skinned." But if you'd rather save some money and you're up for a little knife work, ask for a "peeled, side muscle-on" roast, and trim it yourself as shown at right. You'll need to start with about 4-3/4 pounds to make up for the trim, but the price difference should still be worth it. Our untrimmed roast cost $6 less per pound, saving us about $15 in the end. Another bonus: You can save the chain for cooking another night (think stir-fry). It's perfectly tasty beef, just not as tender as the rest of the tenderloin.
Four Steps to a Trim Tenderloin
1. Locate the chain, the long piece of muscle that runs the length of the tenderloin. (The fatter, shorter, smooth muscle on the other side is part of the loin—leave that on.) Using your fingers, gently separate the chain from the tenderloin as much as possible.
2. With a boning knife, start at the narrow end of the chain and cut along the seam, making several long, shallow cuts rather than one or two deep ones. This way, you have more control over the path your knife takes and less chance of cutting too far in. You don't have to trim every bit of the chain from the wider end; it's fine to leave a narrow strip attached to the loin.
3. Starting about 1 inch from one end of the silverskin, push the tip of your knife under a strip of silverskin about 1/2 inch wide. Using your free hand to hold the silverskin taut, angle the knife slightly up toward the silverskin as you slide the knife down the tenderloin, freeing the silverskin.
4. Turn the knife around and cut off the end of the silverskin that's still attached. Repeat until all the silverskin is gone.