Sweet potato & chicken curry

Ingredients

• 500g sweet potatoes , peeled and cut into bite-size pieces
• 1 tbsp olive oil
• 4 skinless chicken thigh fillets, each cut into large chunks
• 1 large red onion , cut into wedges
• 2 tbsp rogan josh curry paste
• 2 large tomatoes , roughly chopped
• 125g spinach

Method