Cut out the rib from the cavolo nero leaves and discard it, leaving you with long, thin, dimpled ribbons. Fill a wide saucepan (large enough to comfortably hold the cavolo nero) with water to a depth of 4 inches, add a good pinch of salt and bring to a rapid boil. Add the cavolo nero and blanch it for 90 seconds. Drain, then plunge it into iced water or rinse it under a running cold tap. You could do this bit in advance.
Use a vegetable peeler to remove the zest of the orange. Scrape off any white pith from the underside, then cut the fragrant zest into very thin strips. Squeeze the juice and reserve it for later.
When you’re almost ready to eat, set a large frying pan or wok over a medium-high heat. Add 2 tablespoons oil, the chilli, garlic and orange zest. Once the oil starts to bubble around the ingredients, allow them to soften and flavor the oil for 30 seconds more.
Before the garlic starts to color and turn bitter, add the cavolo nero to the pan. The leaves may have become tangled as they drained, so you might need to separate them as you go. Move them around with tongs or a spatula and cook for a couple of minutes, during which time they will soften further and pick up the flavors in the pan. Add the orange juice, remove from the heat and transfer to a serving dish. Pour the remaining oil over the top and season with salt and lots of freshly ground pepper. Mix well so there’s an even distribution of aromatics. Serve immediately.