2 kg (4 lb 8 oz) cavolo nero leaves
Maldon salt and freshly ground black pepper
4 garlic cloves, peeled
250 ml (8 fl oz) extra virgin olive oil
500 g (1 lb 2 oz) penne
Parmesan, freshly grated
For six
Remove the tough stalks of the cavolo nero leaves. Keeping the leaves as whole as possible, blanch them in a generous amount of boiling salted water with 2 garlic cloves for 5 minutes only. Drain well. Put the blanched garlic and cavolo nero in the food processor and pulse-chop to a coarse purée. In the last couple of pulses, pour 75 ml (2.1/2 fl oz) of the extra virgin olive oil into the processor. This makes a dark green liquid purée.
Crush the 2 remaining garlic cloves with 1 teaspoon salt. Stir into the purée along with a further 75 ml (2.1/2 fl oz) oil. Season to taste.
Cook the penne in a generous amount of boiling salted water, then drain thoroughly. Put the pasta into the sauce and stir until each piece is thickly coated. Pour in the remaining olive oil and serve with the Parmesan.