- 450g/1lb hot mashed potatoes (oven-baked until tender, peeled, passed through a potato ricer)
- 10g/¼oz plain flour
- 3 free-range egg yolks
- ½ tsp sea salt
- 25g/1oz butter
- 25g/1oz plain flour
- 750ml/1¼ pints milk
- 1 shallot, peeled, thickly sliced
- 1 fresh bay leaf
- 4 black peppercorns
- 1 clove
- 1 tsp olive oil
- 2 tbsp chopped fresh chervil
- 15g/½oz bone marrow
- 30g/1oz butter
- 150g/5oz brioche breadcrumbs
- 200g/7oz mixed wild mushrooms
- salt and freshly ground black pepper
- 2 x 700g/1lb 8oz cöte de boeuf (bone-in rib of beef)
- 1 tsp olive oil
- 1 head cavolo nero, leaves only
- 50g/2oz butter
- 2 shallots, peeled, finely sliced
- For the gnocchi, mix all of the gnocchi ingredients together until well combined as a dough, using your hands. (Do not overwork the mixture.)
- Turn out the dough onto a lightly floured work surface and roll out to a 0.5cm/½in thickness. Cut the dough into 1.5cm x 3cm/½in x 1in pieces.
- Bring a pan of salted water to the boil. Carefully lower the gnocchi into the pan, in batches, then blanch for 1-2 minutes.
- Drain well and place onto a lightly oiled baking tray. Chill in the fridge until needed.
- For the white sauce, preheat the grill to its highest setting.
- Heat the butter in a saucepan over a low to medium heat until melted. Whisk in the flour until smooth and well combined. (This is called a roux.) Remove from the heat and set aside to cool.
- Bring the milk to the boil in a separate pan. Add the remaining white sauce ingredients except the chervil, then remove the pan from the heat and set aside for 20 minutes to infuse.
- When the milk has infused, pass the it through a fine sieve into a clean saucepan (discard the sieve contents). Whisk the cooled roux into the hot milk and continue to heat until the mixture is boiling and has thickened. Continue to boil for 1-2 minutes, then remove the pan from the heat.
- Meanwhile, for the bone marrow crust, heat the bone marrow and butter in a saucepan over a medium heat until melted and well combined. Remove from the heat, then stir in the brioche crumbs. Set aside.
- For the mushrooms, heat the oil in a frying pan over a medium heat. Add the mushrooms and fry for 1-2 minutes, or until softened. Season, to taste, with salt and freshly ground black pepper.
- Transfer the gnocchi to an ovenproof dish and pour over the white sauce. Stir in the cooked mushrooms and chervil until well combined. Spoon over the bone marrow crust.
- Place the ovenproof dish onto a baking tray and grill until golden-brown and bubbling.
- Meanwhile, for the cöte de boeuf, preheat the oven to 200C/400F/Gas 6.
- Rub the beef all over with the oil, then season on both sides, to taste, with salt and freshly ground black pepper.
- Heat a griddle pan over a high heat until very hot. When the pan is hot, add the beef and fry on both sides for one minute, or until golden-brown chargrill marks appear on both sides of the beef.
- Transfer the griddled beef to a roasting tray and roast in the oven for 12-14 minutes (for rare), or until cooked to your liking. Remove from the roasting tray and set aside on a warm plate to rest for at least five minutes.
- For the cavolo nero, blanch the cavolo nero leaves for 20-30 seconds in a pan of salted, boiling water. Drain well.
- Heat the butter in a frying pan over a medium heat. When the butter is foaming, add the shallots and blanched cavolo nero and fry for 1-2 minutes, or until the cavolo nero is wilted and the shallots have softened.
- To serve, carve the cöte de boeuf into thick slices and divide them equally among four serving plates. Spoon the bone marrow gratin and cavolo nero alongside.