2. Heat an ovenproof frying pan, large enough to fit the steak, over a high heat.
3. Season the steak all over. Add the olive oil to the pan and then sear the steak on all sides to achieve a good dark-brown crust.
4. Place in the oven and cook for 10 minutes per 500g for rare. If you have a thermometer, you can check this – the inside temperature should be 55°C (130°F), 60°C (140°F) for medium rare, 65°C (150°F) for medium well and 70°C (160°F) for well done.
5. Remove from the oven and cover loosely with tin foil. Leave to rest for 15–20 minutes.
6. Meanwhile, preheat the deep-fat fryer to 170°C (325°F).
7. Peel the onion and cut into 1cm slices, then separate into rings and place in a bowl of cold water to soak for 30 minutes.
8. In a food processor, pulse the Rice Krispies to a thick crumb. Put the Rice Krispies and instant mashed potato in a bowl and mix.
9. Put the flour and the spices in a separate bowl and mix well. Drain the onion rings and then remove the transparent skin membrane.
10. Working in small batches, toss the onion rings in the spiced flour mixture and coat in the tempura batter, then toss in the Rice Krispie mixture.
11. Deep-fry for 2–3 minutes until crisp and golden brown. Remove with a slotted spoon and drain on kitchen paper and season with salt and curry powder. Keep warm in a low oven.
12. Place the rested tomahawk on a chopping board and drizzle over the green chimichurri. Add a large pile of the onion rings to the side and a bowl of the triple-cooked chips.
