Fill the kettle and boil it. Tip the rice into a small pan. Pour in 300ml hot water from the kettle. Add a pinch of salt. Cover and bring to the boil. Turn the heat right down. Simmer for 20-25 mins. Take off the heat. Steam, lid on, for 5 mins till the rice is cooked.
Peel and finely slice the onion. Rinse and finely slice the mushrooms. Rinse and pat dry the parsley. Roughly chop it. Rinse the cavolo nero. Trim off any rough ends. Finely shred the leaves.
Warm a splash of olive oil in a deep frying pan or wok. Add the pork. Stir-fry for 8-10 mins till browned and cooked through. Lift out of the pan. Pop on a plate. Put to one side.
Add the onions and mushrooms to the pan. Cook for 5-8 mins till the veg are soft and golden. Stir every so often so they don't catch and burn.
While the veg cooks, tip the cavolo nero into a pan. Cover with hot water from the kettle. Bring to the boil. Turn the heat down. Simmer, without the lid on, for 5 mins or till tender.
Turn the heat under the mushrooms down. Stir in the crème fraîche. Add a pinch of cayenne. Add the pork to the pan with any juices. Stir. Cook gently for 2 mins till hot.
Taste the Stroganoff and adjust the seasoning if you think it needs it. Drain the cavolo nero. Serve the Stroganoff with the rice and cavolo nero, sprinkled with the chopped parsley.