How to Fillet Meat: Tenderloin, Pork Loin and Lamb Leg

To fillet meat cleanly, use a sharp, flexible boning knife about 6 inches long, keep the meat cold (just above freezing is ideal), and follow the seams and bones instead of cutting straight lines. If the meat has sat out more than 20 minutes, put it back in the fridge for 15 minutes before you cut. The method is the same on a beef tenderloin, a bone-in pork loin or a lamb leg.

Why your cuts come out ragged

You're halfway down a tenderloin, the blade is dragging, and the edge of the steak looks chewed. That almost always comes from a wrong or dull knife, warm meat, or cutting across the muscle instead of along it.

Follow the seam, not a straight line.

Every muscle is separated from its neighbor by a thin layer of fascia. Work along that seam and the blade glides while the muscle almost falls away on its own. Cut across it and you need force, you get ragged edges, and one portion ends up holding several muscles that tighten at different rates in the pan.

A chef's knife is too wide and too stiff to get into seams or ride along a bone. A boning knife's narrow, slightly flexible blade lets you feel cartilage and bone through the handle, and feeling that resistance is the whole skill. Your other hand does the same job from the outside, tracking the edge of the bone so the knife knows where to go.

Sharpen before you start. A dull blade tears fibers instead of separating them and needs more pressure, which is exactly when knives slip. Cold matters for the same reason. Warm, soft meat compresses under the blade and gives you uneven thickness, while cold meat holds its shape. Set a damp towel under the board so it can't slide, and keep paper towels nearby for grip. The USDA says raw meat belongs at 40°F or below and shouldn't sit out longer than 2 hours, so work in batches if you're slow.

Related: Sharpen Knives at Home (3 Methods, Ranked by Cost)

How to break down a whole tenderloin

Start here. A beef tenderloin has no bones and clearly defined muscles, so you can learn seam work without a skeleton in the way. In a brigade kitchen it arrives whole and gets cleaned and portioned before service, because whole cuts cost less per pound and the cook controls every portion. At home it's worth doing when you're feeding a crowd or freezing steaks. For one dinner for two, skip it and buy cut filets.

1. Remove the chain. The chain is the long, thin strip running down one side, held on by a thin layer of connective tissue. Pull it gently away from the main muscle and use the knife tip to release the tissue as you go.
2. Peel the silverskin. This iridescent connective tissue doesn't break down with heat, so it shrinks in the pan and makes the meat curl and cook unevenly. Slide the tip under one end, angle the blade slightly up toward the silverskin, and work it off in long strips with a smooth back-and-forth motion. Keep the angle shallow, since you're removing tissue, not protein.
3. Trim the loose fat. Leave a thin exterior layer for flavor and moisture. Take off large, loose deposits, which won't render properly in a pan and cause flare-ups on a grill.
4. Portion the center. The tenderloin has three sections: the thick head (chateaubriand), the center cut (filet mignon or tournedos) and the thin tail. Cut the center into medallions at the thickness you plan to cook. A 2-inch filet behaves very differently on heat than a 1-inch one, so decide on the cooking method first.
5. Tie the tail. Fold the thin tail back on itself and tie it with butcher's twine into an even cylinder, then portion it. Two minutes of tying keeps one end from overcooking while the other stays raw. The head can be roasted whole or butterflied.
6. Dry before cooking. Pat every portion completely dry with paper towels. A wet surface steams instead of browning.

Your first tenderloin will take longer than you expect and the portions won't match. By the third, they will.

What about bone-in pork loin and lamb leg?

Pork loin is the next step because it adds bone. Lay it rib side up and run the boning knife along the curved surface of the ribs, keeping the blade pressed against the bone the whole way. The goal is to lift the loin off the rack in one clean pass without gouging the meat.

You end up with two cuts that cook in opposite ways. The boneless loin can be rolled and tied, stuffed and roasted, or cut into chops at whatever thickness you want. The ribs are hard-working muscle and need low, slow heat on a smoker or in a braise.

A lamb leg uses the same rule with a harder path. Work slowly around the femur and the hip socket, blade always on the bone. Once the bone is out, butterfly the leg flat for the grill or roll and tie it into a compact roast that cooks evenly edge to edge.

This method stops at red meat and pork. Poultry and fish have their own anatomy and their own knives, so use the chicken method or the fish method instead.

Where the trim goes

None of the trim needs to go in the bin. The tenderloin chain works for stir-fries or grinding. Fat trim renders into cooking fat, and lean scraps go into stock or ground meat.

Whole cuts also hold moisture better in storage because they have less exposed surface. Portion close to when you cook, or wrap each piece tightly or vacuum seal it.

Related: Bone Stock at Home Starts With Cold Water

If you're buying a whole tenderloin for a holiday roast, break it down the day before, keep the head and center for the roast, and wrap the tied tail and the chain for weeknight dinners.