The combination of cavolo nero and nuts works magnificently in a winter pesto. Sturdy cavolo nero stands in for summer-y basil leaves, while a handful of almonds is a good replacement for more expensive pine nuts
Strip the leaves off of the cavolo nero and remove the fibrous stalks. Rinse the leaves under running water and gather them in a large pan with two tablespoons of oil and a whole clove of garlic. It will seem like a lot of cavolo nero, but it tends to shrink. You don’t need to preheat the oil.
Cook the cavolo nero over medium heat, turning it often with a wooden spoon, for about 5 minutes, until it softens. Remove the cavolo nero from the pan and let it cool down.
Toast the almonds in a pan for about 5 minutes, tossing them often. Let them cool down, too.
Transfer the cavolo nero to a food processor, along with the almonds. Blend, adding the olive oil in a thin stream, until you get a smooth and thick, dark green pesto.
Scrape the pesto into a bowl, add the grated pecorino cheese, and season with salt, if necessary. If it is still too thick, add more olive oil.
Use it immediately or keep it in the fridge for a couple of days, covered with a film of olive oil to prevent it from blackening.
If you want to use the cavolo nero pesto to dress pasta, put a few tablespoons of pesto in the bottom of a bowl and dilute it with some pasta water, to emulsify it into a sauce, then toss in the pasta.