Westphalian Leg of Lamb

This Westphalian leg of lamb comes from the northwest German tradition of braising meat in buttermilk, a technique that produces some of the most tender, tangy roast lamb you’ll ever taste. The acid in the buttermilk slowly breaks down the proteins as the lamb roasts, making even tougher cuts melt-in-your-mouth soft.

The oven bag is the secret weapon. It traps all the moisture and buttermilk steam inside, essentially braising and roasting at the same time. Sautéed onion, carrot, and parsley go into the bag with the lamb, infusing the buttermilk into an aromatic cooking liquid that becomes gravy.

After roasting, you strain the bag juices and thicken them with a cornstarch slurry into a silky, tangy sauce. That buttermilk gravy is unlike anything you’ve had on lamb before. It’s lighter and brighter than a traditional pan jus, with a subtle tang.

Use a meat thermometer and don’t guess. The bag makes it hard to judge doneness by look or touch alone.

Kitchen Tips

• Puncture the oven bag 3-4 times to vent steam. Without vents, pressure builds and the bag can burst.
• Dust flour inside the bag before adding ingredients. It prevents the bag from sticking and helps thicken the juices slightly.
• Sauté the vegetables until the onion is truly transparent, not just softened. This develops deeper flavor in the sauce.
• Let the lamb rest 15 minutes after removing from the bag so juices redistribute before carving.

Variations

• Herb-crusted: Rub the lamb with a paste of rosemary, garlic, and mustard before bagging for a more aromatic crust.
• Wine version: Replace half the buttermilk with dry white wine for a less tangy, more traditional European flavor.