• 4 brown onions
• grapeseed oil, for frying
• 680 g (1 lb 8 oz) aged beef tenderloin, at room temperature

Bone Marrow Croquettes

• 2 large veal bones, cut lengthways
• 2 tablespoons finely chopped flat-leaf (Italian) parsley
• 70 g (2½ oz/½ cup) plain (all-purpose) flour
• 1 egg, lightly beaten
• 110 g (3¾ oz/1 cup) dry breadcrumbs, to coat
• vegetable oil, for frying

Potato Fondant

• 225 g (8 oz) unsalted butter
• 4 kennebec potatoes, peeled, trimmed into four rectangular blocks

Red Wine Sauce

• 1 tablespoon chopped shallots
• 1 tablespoon black pepper, freshly cracked
• 1 tablespoon pink peppercorns, freshly cracked
• 30 ml (1 fl oz) brandy
• 120 ml (4 fl oz/½ cup) red wine
• 60 ml (2 fl oz/¼ cup) thick (double) cream

Preheat the oven to 200°C (400°F/Gas 6). Season the veal bones generously with salt and pepper. Place on a baking tray and roast for 10–20 minutes or until the marrow is golden and cooked. Set aside to cool. Once cooled, remove the marrow and combine with the parsley in a small bowl. Form the mixture into 4 uniform balls, cover and chill in the refrigerator until firm.

Put the flour, egg and breadcrumbs in separate bowls. Lightly coat the marrow croquettes in the flour, then in the egg and finally in the breadcrumbs. Put the croquettes on a baking tray lined with baking paper and place in the refrigerator.

Put the onions in their skins on a baking tray and cook in the oven for 30 minutes or until completely cooked through. Peel the onions and cut in half. Put a heavy-based ovenproof frying pan over medium heat and add a small amount of grapeseed oil. Cook the onions, cut side down, until lightly charred. Set aside.

Meanwhile, for the potato fondant, heat a frying pan over medium heat. Add the butter and cook until foaming. Add the potatoes and season generously with salt. Increase the temperature until the butter foams around the potatoes, and adjust the heat as necessary to maintain this foam. Cook the potatoes on all sides until crisp and golden. Remove the pan from heat, add the charred onions and allow the potatoes and onions to stand in the hot butter until ready to serve.

Reduce the oven temperature to 150°C (300°F/Gas 2). Using the same frying pan that you used for the onions, season the tenderloin and sear it on all sides, then put the pan into the oven for 10 minutes or until cooked to your liking. Remove the tenderloin from the pan and set aside to rest.

Add the shallots and combined cracked pepper to the meat drippings and flambé with the brandy and wine, then cook over low heat until reduced. Strain through a fine sieve into a clean saucepan, return to the pan and add the cream.

Preheat the vegetable oil in a deep-fryer or large, heavy-based saucepan to 180°C (350°F) or until a cube of bread dropped into the oil turns brown in 15 seconds. Carefully fry the croquettes for 2–3 minutes or until golden. Remove the potatoes and charred onions from the warm butter and drain on paper towel, separating the onions into their petals.

Carefully slice and plate the tenderloin with the potato fondant and a bone marrow croquette, scatter with the charred onion and carefully spoon the red wine sauce over the beef. Serve immediately.