Preheat your oven to 200°C (180°C fan).
In a bowl, mix the harissa paste with olive oil and a pinch of salt and pepper. Rub the mixture all over the chicken thighs.
Place the onion wedges, sliced peppers and chickpeas in a large roasting tray, I use a large roasting tray like this one so everything has space to roast and caramelise nicely. Drizzle with a little oil and season. Toss to coat, then nestle the chicken thighs on top. Roast for 35–40 minutes, or until the chicken is golden and cooked through and the veg is soft and slightly charred at the edges.
Squeeze over a little lemon juice, sprinkle with chopped herbs, and serve with a dollop of yoghurt if you like. A small citrus juicer like this makes it easy to get every last drop of juice over the tray at the end.