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Roast Leg of Lamb with Fennel Butter

Peer reviewed by UK recipe editorsAuthored by UK recipe editorsOriginally published 17 Jan 2026

Meets Patient’s editorial guidelines

This classic roast leg of lamb with fennel butter is a sophisticated choice for a Sunday roast or a celebratory family Easter lunch. The lamb is first seared to lock in moisture, then roasted with a punchy aromatic butter made from crushed fennel seeds, Dijon mustard, and garlic. As the meat rests, the roasting juices are transformed into a rich, savoury red wine reduction that perfectly complements the earthy notes of the rosemary and fennel.

While the recipe calls for a bone-in leg to ensure maximum flavour and succulence, it remains a relatively simple dish to prepare. Serving this alongside seasonal greens and crisp roast potatoes makes for a balanced, heart-healthy meal that provides a modern twist on traditional British roasting techniques. The seasoned butter can even be prepared a day in advance for a stress-free hosting experience.

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Ingredients for Roast Leg of Lamb with Fennel Butter

  • 90ml (3/4 stick) butter, room temperature

  • 3 tablespoons fennel seeds, crushed in plastic bag with mallet

  • 3 large garlic cloves, minced

  • 2 tablespoons Dijon mustard

  • 1 1/2 tablespoons soy sauce

  • 1 tablespoon coarsely ground black pepper

  • 1 1/2 teaspoons dried crushed rosemary

  • 2 tablespoons olive oil

  • 1 6- to 2.9kg bone-in leg of lamb, well trimmed

  • 475ml dry red wine

  • 325ml low-salt chicken broth

  • Fresh rosemary sprigs (optional)

How to make Roast Leg of Lamb with Fennel Butter

Mix all ingredients with fork in medium bowl. (Can be made 1 day ahead. Cover and refrigerate. Bring to room temperature before using.)

Position rack in bottom third of oven and preheat to 232°C. Pour 2 tablespoons oil into large roasting pan. Place pan directly atop 2 burners over medium-high heat. Sprinkle lamb with salt and pepper. Add lamb to pan and brown on all sides, about 8 minutes total. Remove pan from heat. Brush lamb with half of seasoned butter.

Roast lamb 30 minutes. Reduce heat to 177°C; continue roasting until thermometer inserted into thickest part of meat registers 54°C for medium-rare, about 40 minutes longer. Transfer to platter; tent with foil. Let stand 20 minutes.

Skim off fat from drippings in roasting pan. Place pan atop 2 burners over high heat. Add wine and broth. Boil until mixture is reduced to 475ml , about 13 minutes. Whisk in remaining seasoned butter (sauce will be thin). Season sauce to taste with salt and pepper.

Garnish lamb with rosemary sprigs, if desired. Serve with sauce.

Disclaimer

While every effort has been made to ensure the information is accurate and up to date, individual needs may vary and dietary requirements can differ based on personal health conditions. Always check food labels and allergen information before preparing or consuming any recipe. If you have specific health concerns, allergies, intolerances, or are following a medically prescribed diet, seek advice from your GP, pharmacist, or a registered dietitian before making significant changes to your diet or lifestyle.

Article history

The information on this page is peer reviewed by qualified clinicians.

  • 17 Jan 2026 | Originally published

    Authored by:

    UK recipe editors

    Peer reviewed by

    UK recipe editors
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