1 medium butternut squash, halved, peeled, deseeded and sliced into 4cm-thick wedges
4 small red onions, quartered
2 lemons, zested and juiced
1 tsp fennel seeds
1 tsp smoked paprika
For the sauce
2 garlic bulbs
1 tbsp olive oil, plus 2 tsp extra
2 shallots, finely chopped
2 tbsp Belazu sherry vinegar
300ml dry sherry
500ml beef stock
2 tbsp double cream
⅔ x 30g pack flat-leaf parsley, finely chopped
Preheat the oven to 200°C, fan 180°C, gas 6. Remove the top third of each garlic bulb and discard it for the sauce. Drizzle 2 tsp oil over the bulbs, enclose in foil, and roast for 45 minutes or until golden brown. Set aside.
Make a deep, lengthwise cut in the beef so that it opens like a book, but don't go all the way through. In the center, arrange the spinach, chorizo, cumin seeds, and dates, then tightly roll up the beef to contain the filling. Tighten the knots with kitchen string.
In a large frying pan, heat 1 tablespoon of oil over medium heat. Season the meat and sear for 4-5 minutes, turning frequently, until deep brown on all sides.
Put the beef in a roasting pan. Reduce the temperature to gas 4, 180°C, fan 160°C after 15 minutes of roasting. For medium-rare, cook for an additional 1 hour and 20 minutes. Cook for 1 hour 40 minutes for medium, and 2 hours for well done. Cover with foil and set aside to rest for 30 minutes once cooked to your satisfaction.
In the meantime, arrange the squash and onions on a large baking sheet. Toss with the lemon zest, juice, 2 tablespoons oil, spices, and salt and pepper to taste. Roast for 30-40 minutes, until brown and soft, stirring halfway through.
To create the sauce, in a frying pan over medium heat, heat 1 tbsp oil and sauté the shallots for 5 minutes, or until tender. Remove the skins from the roasted garlic bulbs and squeeze the garlic into the pan. Season and add the sherry vinegar, sherry and stock, then simmer over a medium heat for 10 mins to reduce by half. Season to taste with the cream and parsley. Carve the steak and serve it with the squash and onion wedges, as well as the sauce.