Chicken and spinach bake

INGREDIENTS 6-8 chicken pieces 2 tbsp :     olive oil  30g butter 100g :     leeks, roughly chopped 150g :     mushrooms, halved 250g :     cherry tomatoes 1 tbsp :     soft brown sugar 2 tbsp :     balsamic reduction* 100g :     baby spinach leaves 200g :     canned chickpeas, drained (about 1/2 a can) salt and freshly ground black pepper PREPARATION 1. Preheat oven to 180°C. Season chicken with salt and pepper. Heat oil and butter in a pan and brown chicken. Transfer to an oven-proof dish. 2. In the same pan, fry leeks and mushrooms for a few minutes then spoon over chicken. Scatter tomatoes on top. 3. Sprinkle over sugar and balsamic reduction then bake for 30 minutes. Add spinach and chickpeas. Bake for another 5-10 minutes. Remove from oven, allow to cool a little, then serve.