BBC Food - Recipes - Mozzarella chicken with butter bean mash

Ingredients

• 4 chicken breasts , boned and skinned
• calorie controlled cooking oil spray
• 1 medium onion , thinly sliced
• 2 garlic cloves, crushed
• 400g tin chopped tomatoes
• 3 tbsp tomato purée
• 1½ tsp dried oregano
• 85g/3oz pitted green or black olives
• 2 x 125g packs reduced fat mozzarella , sliced and drained on kitchen paper
• 1 medium onion , finely chopped
• 1 garlic clove, crushed
• 2 x 400g tin butter beans , drained
• good squeeze lemon juice
• sea salt and freshly ground black pepper