Put a large pan of salted water on to boil. Pour the tamari into a dish. Grate in the zest from the lemon. Squeeze in the juice from one half. Peel and grate in the garlic clove. Add 1 tsp each cumin and oregano and a pinch of cayenne (the cayenne is spicy, so use less or more depending on how hot you want your final dish). Stir to mix together.
Add the chicken to the marinade. Turn to coat all over. Set aside to marinate while you prepare the potatoes.
Scrub the potatoes and chop them into chunks around 2cm across. When the water in the pan is boiling, add the potatoes. Turn the heat down a little and simmer for 15 mins till the potatoes are tender when pressed with a fork.
While the potatoes simmer, finely chop the parsley leaves and stalks. Pop them in a bowl. Stir in the crème fraîche, along with a pinch of salt and pepper. Set aside.
Trim the dry ends off the cavolo nero and finely shred the leaves. Quarter the cherry tomatoes.
Warm a griddle or frying pan over a high heat for 2 mins. Add ½tbsp oil and the chicken. Griddle for 10-12 mins, turning the chicken every so often, till it’s lightly charred and cooked through – there should be no pink meat if you cut through the thickest part of the chicken fillets. Take out of the pan and pop on a plate. Loosely cover with foil and set aside to rest.
Add the cavolo nero and cherry tomatoes to the pan with ½ tbsp olive oil and griddle for 5 mins, turning, till the tomatoes are soft and the cavolo nero has wilted.
The potatoes should be ready by now. Drain them, then return to the pan. Use a masher to gently squash the potatoes so they are crushed and break. Add half the crème fraîche sauce and toss to mix.
Serve the chicken with the crushed potatoes, griddled chicken, tomatoes, cavolo nero and the remaining crème fraîche sauce.