Preheat the oven to 200ºC, line a roasting tray with baking parchment and place the sweet potatoes in the oven for 40-50 minutes until tender. Remove when cooked and leave to cool.
Wilt the spinach in a pan with a little water and leave to cool in a sieve. Squeeze out excess water, coarsely chop and set aside.
When cool, halve the sweet potatoes and scoop the flesh into a large bowl. Mash until smooth, add the chopped spinach, egg yolks, salt and mix well.
Add the flour in small batches until you have a workable dough (You may not need to add all the flour).
On a floured surface, divide your dough into 4 and roll each portion into a log about 1.5cm thick. Cut into individual pieces around 2cm long. Once shaped, place on a tray and then into the fridge for about 30 minutes to firm up.
Bring a large pan of salted water to the boil. Add the cavolo nero and boil for 3-4 minutes. Remove and leave to cool slightly – keeping the water. When cooled, roughly chop.
Remove the gnocchi from the fridge. Gently place the gnocchi into the water and cook until they rise to the surface (should take 2-4 minutes). Cook these in batches so they don’t stick together; then, using a slotted spoon, remove the gnocchi from the pan and onto a cooling rack to dry.
In a large frying pan, cook the garlic in Filippo Berio Classico Olive Oil on a low heat for 2 minutes. Add the chilli and cook for a further two minutes.