Heat oven to 220C/200C fan/gas 7. Pop the chicken, skin-side up, in a large roasting tin with the potatoes. Lightly crush the garlic cloves and nestle among the chicken pieces. Drizzle over the olive oil and chicken stock, then season. Squeeze over the juice from the lemon and pop the empty halves in the tin.
Bake for 45-50 mins, adding the courgettes and chilli 15 mins before the cooking time is up. Remove from the oven when the chicken is cooked through and golden, and the veg is tender. Stir through the basil leaves and serve.