Chop the chicken breast mini fillets into bite-size chunks. Warm 1 tsp olive oil in a medium pan over a low heat. Add the chicken. Gently fry for 5-6 mins till the chicken is browned all over. Turn once or twice while it cooks.
While the chicken cooks, peel and finely chop the onion. Peel and finely chop the carrot. Rinse and finely slice the celery. Rinse and halve the peppers. Scoop out the seeds and white bits. Roughly chop the peppers.
Add the onion, carrot, celery and peppers to the chicken. Season with a pinch of salt and pepper. Fry over a medium heat for 5 mins till the veg look soft and glossy. Stir every so often. If you think they’re sticking, add a splash of water to loosen everything up.
Fill a kettle and boil it. Halve the squash. Scoop the seeds out of one half. Peel it. Chop it into small chunks. Peel and grate or crush the garlic. Stir the squash and garlic into the veg.
Add a small pinch of cayenne pepper to the pan. Measure out 1 tsp each of the paprika, cumin and fennel seeds. Add to the pan. Cook and stir for 1 min.
Pour 700ml hot water into the pan. Pop on the lid. Bring to the boil, then turn the heat down. Simmer for 15 mins till the chicken is cooked through and the squash is soft. While the soup simmers, rinse the cavolo nero. Trim the ends off and finely shred the cavolo nero leaves.
Add the cavolo nero to the pan. Give everything a stir. Simmer, without the lid on, for 4-5 mins till the cavolo nero is tender. Taste and add more salt, pepper, cayenne or smoked paprika if you think it needs it. Ladle into warm bowls and serve straight away.