Make the shapta sauce first. Heat the rapeseed oil over a medium heat, add the garlic and chilli flakes and saute. Add the soy sauce, Szechuan pepper powder, black pepper powder and sugar, followed by the tomato sauce or ketchup.
Add the water and simmer for 3-4 minutes, then remove from the heat.
Heat the oven to 180C (fan 160C). Cook the lamb fillets in the oven for 12 minutes, then remove to a tray lined with kitchen paper.
After 3-4 minutes, slice the lamb fillets ready for serving.
Heat the 2 tablespoons of rapeseed oil in a wok and saute the garlic and whole red chillies.
Add the peppers and cook for 1-2 minutes, then add the shapta sauce.
Add the spring onion greens and bok choi and saute for 2-3 minutes, then add the ginger strips.
Divide between serving plates and top with the sliced lamb fillet.