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Grilled Sweet Onion and Butter Sandwich

Peer reviewed by UK recipe editorsAuthored by UK recipe editorsOriginally published 28 Jan 2026

Meets Patient’s editorial guidelines

This grilled sweet onion and butter sandwich is a masterclass in simplicity, proving that a few humble larder staples can be transformed into something truly special. By using a circular cutter, you create elegant, crustless rounds that crisp up beautifully in the frying pan, offering a satisfying crunch that contrasts with the gentle bite of the filling. The sweet onion softens just enough during the brief cooking time to lose its sharp edge, melding perfectly with the melted unsalted butter.

Ideal as a sophisticated vegetarian lunch or a quick afternoon snack, these golden sandwiches rely on quality ingredients for their superior flavour. A generous seasoning of flaky sea salt and a scatter of fresh parsley adds a brightness that cuts through the richness of the butter. Serve them warm from the pan while the bread is at its crispest and the centre remains beautifully soft.

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Ingredients for Grilled Sweet Onion and Butter Sandwich

  • 8 slices white sandwich bread

  • 4 tablespoons unsalted butter, room temperature

  • 1/2 small sweet onion, sliced into 1/8-inch-thick rounds

  • Flaky sea salt

  • Coarsely ground black pepper

  • Chopped parsley (for serving)

  • A 3 1/2-inch-diameter biscuit cutter

How to make Grilled Sweet Onion and Butter Sandwich

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Using cutter, punch a round from each slice of bread. Spread both sides with butter and top 4 rounds with 2 onion slices each; season with salt and pepper. Close sandwiches.

Heat a large skillet, preferably nonstick, over medium-high and cook sandwiches until golden brown, about 2 minutes per side (onion will soften slightly). Top with parsley and more salt.

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.

  • 28 Jan 2026 | Originally published

    Authored by:

    UK recipe editors

    Peer reviewed by

    UK recipe editors
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