- Preheat oven to 160C.
- Pour beef stock into a large saucepan and bring to boil over medium-high heat. Continue to cook until the stock has reduced by half and is now 1 litre (this should take 15-20 minutes) Using this reduced stock will make the final dish richer and more delicious.
- Place a frying pan over medium-high heat and add 1 tbsp of coconut oil. Add dice steak pieces and cook for 2 1/2 minutes on each side, or until they are nicely browned. Remove from the heat and set aside.
- Melt the remaining coconut oil in an ovenproof casserole dish over medium heat. Add the garlic and cook for 2 minutes, or until soft. Add the onion, rosemary, chilli and a small pinch of salt. Stir well and cook for a few minutes, or until the onion is soft. Add the carrot and celery, stir well and cook for a further 2 minutes. Stir in the tomato paste and cook for 2 minutes. Add the tomatoes and stir well. Remove from the heat.
- Place the rump steak and cauliflower in the casserole dish and pour over the stock. Cover first with a sheet of baking paper, then with a tight-fitting lid. Cook in the oven for 2 hours. Add the cavolo nero and return to the oven to cook for another 5 minutes, or until the cavolo nero is just wilted.
- Season with salt and pepper to taste and serve.