For the harissa, place all the harissa ingredients into a food processor and blend to a smooth paste. Spoon the harissa into a jar and store in the fridge until ready to use.
For the stew, slash the chicken thighs several times then place into a bowl with three tablespoons of the harissa paste and mix until well combined. Marinate in the fridge for at least two hours.
Preheat the oven to 180C/350F/Gas 4.
Heat the olive oil in a flameproof casserole until hot, add the chicken thighs and cook for 3-4 minutes, turning regularly, or until browned all over. (You may need to do this in batches.) Remove the chicken thighs from the pan and set aside.
Add the onions to the pan and cook for 3-4 minutes, or until just softened.
Add two tablespoons of the harissa paste and cook for one minute, then add the potatoes and stir until coated in the paste. Add the tinned tomatoes and stock and bring to the boil.
Return the chicken to the pan and bring back to a simmer.
Place in the oven and cook for 45-55 minutes, or until the chicken is cooked through and tender and the sauce is slightly reduced. Stir in the lemon juice and parsley and season, to taste, with salt and freshly ground black pepper.
For the herby chicken salad, whisk the crushed garlic, vinegar, honey, lemon juice and oil together in a bowl until emulsified then season with a little salt and freshly ground black pepper.
Place the remaining ingredients into a bowl and mix together. Add the dressing and mix until well combined.
To serve, spoon the chicken stew onto serving plates and spoon some salad alongside.