Slow-cooked chicken puttanesca

Ingredients

• 3 tbsp olive oil
• 1 onion, sliced
• 2 garlic cloves, crushed
• ½ tsp chilli flakes
• 1 tbsp dried oregano
• 2 x 400g tins chopped tomatoes
• 120g pitted black olives
• 6 anchovy fillets, finely chopped
• 2 tsp capers, rinsed
• 8 skin-on, bone-in free-range chicken thighs
• Small bunch parsley, finely chopped
• Creamy mashed potatoes or cheesy polenta to serve