For me, the best way to cook a whole chicken on the barbecue is to be safe and cook it blonde in the oven first – then finish it on the barbecue to get that crispy, golden skin and let that smoky flavour penetrate right through.
To make the marinade, peel and finely chop the onion. Peel and smash the garlic, then pick and finely chop the rosemary leaves. Mix together in a large bowl with the bay and vinegar. Set aside.
Slash the chicken across each leg about 3 or 4 times – this will allow the heat to penetrate directly into the meat and help it cook faster. Place the chicken in the marinade, rubbing the flavour all over. Cover and leave in the fridge for at least 12 hours.
When you're ready to cook, preheat the oven to 190ºC/375ºF/gas 5. Fire up your barbecue.
Remove the chicken from the brine and pat dry with kitchen paper, then place in a roasting tray. Halve the lemon and pop it inside the chicken’s cavity with the bay leaves from the brine. Cover with a double layer of tin foil and roast in the oven for 1 hour, or until cooked through.
Cut the potatoes into rough 2cm cubes and smash the garlic, leaving the skin on. Pick the oregano leaves. Toss in a large roasting tray with a good splash of olive oil.
Season with sea salt and black pepper and roast alongside the chicken for about 40 minutes, or until lovely and crispy and golden.
After an hour, remove the chicken from the oven and finish on the barbecue, or until beautifully golden and crisp all over, turning occasionally.
Make the French dressing by shaking up the mustard, extra virgin olive oil, vinegar, and a pinch of sea salt and black pepper, in a jam jar.
Pick the inner white leaves from the frisée, discarding the green leaves. Add all the salad greens to a serving bowl, drizzle over the dressing and toss to coat. Serve with the chicken and crispy potatoes.