Heat the oil in a nonstick frying pan over a medium heat. Add the chicken thighs and cook gently, turning frequently until the chicken is cooked through (about 20 minutes).
Meanwhile, make the pesto by placing all the ingredients in a food processor or blender and whizzing until smooth and well combined.
Remove the chicken from the pan and keep hot. Reduce the heat and add the pesto to the pan. Heat through for 2–3 minutes.
Pour the warmed pesto over the chicken thighs, garnish with basil and serve with courgette ribbons and grilled tomatoes.