‘Cavolo nero’ soup with feta cheese and pistachios

Difficulty: Time:  INGREDIENTS (x 6 persons): - 200g Cavolo nero leaves - 2 medium size, white baking potatoes - 1 large sweet white onion - extra virgin olive oil - 2 vegetable stock cubes - black pepper - sumac powder (optional) - 1 handful crunched unsalted pistachios - 150g feta cheese, crumbled WHAT TO DO: 1. Start by carefully rinsing ...