Place the lemon juice, oil, chilli and garlic in a medium glass or ceramic bowl. Season with salt, and whisk to combine, add the chicken and turn to coat, cover with clingfilm and marinate in the fridge for 30 minutes.
Heat the oven to 200°C (gas mark 6). Drain the chicken from the marinade and dry with kitchen paper. Heat a large griddle pan and sear each of the chicken pieces for about 2 minutes on each side. Transfer the pan to the oven (with the chicken skin side up) and roast for about 20 minutes, or until cooked.
Meanwhile, make the piri-piri dressing by putting the vinegar, chillies, sherry and oil in a screw top jar, shake well, and serve with the chicken.
Simply mix the mayonnaise and garlic in a small bowl. Season to taste with salt, and pepper.
Delicious served with spicy rice and grilled vegetables or salad greens.