Dice the onion, carrot and celery into 5mm (¼-inch) cubes. Put the diced vegetables into a saucepan with the olive oil and salt and gently heat. Cook very slowly, taking care not to colour the onions. Chop the garlic and parsley together to create a paste and add to the saucepan. Cook very slowly, for about 30 minutes, until the vegetables are soft.

Meanwhile, empty the cans of tomatoes into a sieve over the sink and gently rinse the sauce from them. Shake dry, then cut into 1cm (½-inch) dice. When the vegetables are cooked, add the chopped tomatoes and any juice they released, and continue to cook gently for 20 minutes. Add the lentils, barley and water. Cook gently for about 30 minutes with a lid on, until the barley is plump and soft and the lentils are cooked. If the mix begins to run dry, add a little more water, but not too much–you want a thick broth.

Add the cavolo nero and cook gently for another 15 minutes until soft, then remove from the heat. Check the seasoning and adjust if necessary.

Spoon the broth into serving bowls and drizzle generously with the best olive oil you can find. Add a twist of black pepper and serve with focaccia.