For the lemon and anchovy butter, place the butter in a bowl and add the lemon zest, anchovy fillets, garlic, coriander seeds and one teaspoon of the harissa. Mash them all together and add the lemon juice bit by bit. Check the seasoning.
Take a double layer of aluminium foil. Place the butter in a long sausage shape at one end and roll it up. Then twist the ends of the foil in opposing directions to form a tight roll. Chill for four hours in the fridge to set.
For the chicken, preheat the oven to 180C/350F/Gas 4.
Season the chicken with salt and pepper and rub the remaining harissa over the skin. Heat a heavy oven-proof pan on the hob along with a splash of oil. Once hot, place the chicken in skin-side down and fry for several minutes until lightly coloured.
Transfer to the oven and cook for 30 to 40 minutes, or until the chicken is cooked through. Remove from the oven and leave to rest for 5-10 minutes in the cooking pan, keeping it warm.
To serve, tear the top leafy part of the watercress from the bunch and put in a salad bowl. Add the almonds, raisins and spring onions. Season with salt and pepper and drizzle over a little olive oil and red wine vinegar. Mix well and pile onto a serving plate. Cut the breasts in half and pile on top of the salad. Finally, melt a few thin slices of the lemon and anchovy butter and drizzle over the chicken.