1. For the venison marinade, in a mixing bowl whisk together the sherry, soy, black pepper, cumin, paprika and half of the wholegrain mustard. Place the venison in the marinade. Marinate for at least one hour, but the longer the better – overnight in the fridge is good.

2. Heat a tablespoon of oil in a heavy-based saucepan. Add the onions and sweat them down for 30 minutes, stirring frequently to prevent sticking. When the onions have visibly changed in colour to a golden brown, add the sugar and 10g of the unsalted butter. Season well with salt and pepper and continue to caramelise for a further 10 minutes till the onions are sticky and a rich brown colour. Remove from pan and set aside.

3. Meanwhile, for the blue cheese butter, mix the rest of the softened butter, garlic, parsley, and the rest of the mustard together and season with salt and pepper. Crumble in the blue cheese, and mash it all together using a fork or a potato mashed. Place in an airtight container and set aside. This butter will also keep for three weeks in the fridge.

4. Remove the venison loin from fridge at least 45 minutes before cooking to allow it come up to room temperature.

5. Using a cast iron skillet or grill, place on a high heat till the pan is almost smoking. Coat the venison lightly in oil and add it to the pan. Sear the meat on each side for three to five minutes for rare; eight-10 minutes for medium rare. Remove it from pan and rest it for 10 minutes.

6. Preheat the grill on medium high. Cut the baguettes lengthways and toast until golden brown. Generously spread the toast with the blue cheese butter. Carefully slice the venison and assemble it on the baguette, add the onions and cut into four portions. Garnish with rocket or watercress.