Heston Blumenthal's bone-marrow sauce recipe

• 2kg beef stock
• 100g unsalted butter
• 250g peeled and finely sliced shallot (approx. 5 banana shallots)
• 150g white wine
• 100g Dijon mustard
• 10g sherry vinegar
• 15g lemon juice
• 100g bone marrow, rinsed and diced (ask the butcher)
• 20g flat-leaf parsley leaves
• 20g chives
• 10g tarragon leaves

Salt and black pepper

1. To start the bone-marrow sauce, pour the beef stock into a large saucepan and place over a high heat. Bring to the boil and allow the liquid to reduce by three-quarters until 500g remains (approximately 25 minutes).
2. In the meantime, melt the butter in a medium saucepan and cook the shallots for approximately 7–10 minutes until they are light brown in colour. Add the wine and allow to reduce by three-quarters.
3. Remove the shallot pan from the heat and add the Dijon mustard. Stir thoroughly before adding the reduced beef stock.
4. Add the sherry vinegar and lemon juice and whisk until all the ingredients are fully incorporated.
5. Gently heat the sauce and when hot, add the diced bone marrow and remove the pan from the heat. The bone marrow should soften but not melt. Finely chop the herbs and stir them into the sauce. Season with salt and freshly ground pepper and pour into a warm jug.