Thinly slice two onions and add them to a wide pan with a generous knob of butter and a drizzle of olive oil. Cook them slowly over low heat, stirring occasionally, until they become deep brown and jammy – this can take around 15 minutes. Add one finely sliced garlic clove and a bay leaf, along with a pinch of salt, and cook for another minute.

Stir in 1 tablespoon of Edmond Fallot White Wine Vinegar, let it sizzle briefly, then pour in 100ml of white wine and 100ml of beef stock. Let the mixture simmer and reduce by about half, concentrating the flavors. Once reduced, remove the onion mixture from the pan and set it aside.

While the sauce reduces, slice 300g of lamb’s liver into thin slivers. Sprinkle with salt and toss with 1 tablespoon of plain flour until lightly coated. Heat a fresh splash of olive oil in the same pan over high heat, then quickly fry the liver slices for about a minute on each side until browned but still pink in the center.

Return the onion mixture to the pan. The flour from the liver will help thicken the sauce slightly as it cooks. Stir everything together and cook for a final 1–2 minutes until glossy and thick. Serve hot with crusty bread to mop up the rich, savoury sauce.