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Grilled Steak and Onions with Rosemary-Balsamic Butter Sauce

This sophisticated grilled steak with rosemary-balsamic butter sauce is an elegant choice for those seeking a diabetes-friendly meal that refuses to compromise on depth of flavour. By pairing lean New York strip steaks with a vibrant medley of charred sweet onions, leeks, and shallots, this dish creates a satisfying balance of textures. The silky balsamic reduction, brightened with a hint of citrus and fresh herbs, provides a luxurious finish that perfectly complements the savoury, smoky notes from the grill.

Ideal for outdoor dining or a refined weekend dinner, this recipe celebrates high-quality ingredients and simple cooking techniques. Using a variety of onions adds a natural sweetness that pairs beautifully with the rosemary-infused butter, making it a wonderful centrepiece for any occasion. Serve this protein-rich dish with a crisp green salad or steamed seasonal greens for a complete, nutritionally balanced meal that feels truly indulgent.

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Ingredients for Grilled Steak and Onions with Rosemary-Balsamic Butter Sauce

  • 8 tablespoons (1 stick) chilled unsalted butter, divided

  • 1 large shallot, minced

  • 120ml balsamic vinegar

  • 2 large fresh rosemary sprigs

  • 900g mixed sweet onions, large shallots, baby leeks, and spring onions

  • 2 tablespoons olive oil

  • 4 (1 1/4-inch-thick) New York strip steaks (each about 170g )

  • 2 tablespoons orange juice

How to make Grilled Steak and Onions with Rosemary-Balsamic Butter Sauce

Melt 90ml butter in heavy small saucepan over medium heat. Add minced shallot and cook until translucent, about 2 minutes. Add vinegar and rosemary and simmer until syrupy and reduced to 120ml , about 6 minutes. Remove from heat (balsamic sauce will separate as it stands).

Prepare barbecue (medium-high heat). Peel sweet onions, then cut into 1/2-inch-thick rounds. Skewer horizontally with toothpicks to keep intact. Peel shallots; cut in half lengthwise. Trim root ends and tops of leeks. Cut in half lengthwise; rinse to remove any dirt. Trim root ends of spring onions. Place sweet onions, shallots, leeks, and spring onions on rimmed baking sheet and drizzle with oil; toss. Sprinkle with salt and pepper.

Sprinkle steaks with salt and pepper. Grill sweet onions, shallots, leeks, and spring onions until tender, turning often, about 5 minutes for spring onions and 10 minutes for sweet onions, shallots, and leeks. Move onions to cooler part of grill to keep warm. Grill steaks to desired doneness, about 7 minutes per side for medium-rare. Transfer steaks and onions to platter; cover.

Remove rosemary sprigs from balsamic sauce; add orange juice and bring to simmer. Remove saucepan from heat; add remaining 2 tablespoons chilled butter and whisk until melted and sauce is smooth. Season sauce to taste with salt and pepper. Drizzle some of sauce over steaks and onions. Serve, passing remaining sauce separately.

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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