Dried porcini mushrooms give this ragout a deep, satisfying taste and are a perfect match with the earthy cavolo nero. It’s best to use black beluga or French puy lentils as they will keep their shape when cooked. Serve on top of a roasted sweet potato, or with your choice of pasta or cooked grain.
Preheat the oven to 200˚C/180˚C/ gas mark 6. Place the sweet potatoes on a baking tray and cook for 45 minutes until tender. Place the dried mushrooms in a heat-resistant bowl and pour over 250ml boiling water, and leave them to rehydrate for 15-20 minutes. Drain and reserve the soaking liquid, then roughly chop the mushrooms.
Wash the lentils in a fine mesh sieve then place them in a pan with 1 litre of water. Bring to the boil with the lid on, then reduce the heat and leave to simmer for 20-25 minutes. Drain any remaining cooking liquid and set aside.
In a pan over a medium heat, cook the mushrooms with their soaking liquid and the garlic. After a minute, add the herbes de Provence and the tomatoes and cook for another 2–3 minutes.
Add the lentils and season with salt and freshly ground black pepper. Bring to the boil, then reduce the heat to low and simmer for 15 minutes. If it looks too dry, add some more water. When the lentils are cooked, add the cavolo nero. Cook for a further 8-10 minutes, until soft and done.
Remove the sweet potatoes from the oven, make a deep slit in the top of each one and open them up a bit. Fill with the ragout and serve immediately.
Use a sieve lined with a clean kitchen towel or muslin cloth to catch the dirt or sand from the mushrooms when draining them after soaking.