Hunter's chicken casserole

Ingredients

• 1 teaspoon olive oil
• 2 x 120g chicken breasts, skinless
• 1 small red onion, sliced
• 1 small red pepper, sliced lengthways
• 1 small courgette, sliced
• 1 medium carrot, sliced
• 1 clove garlic, finely diced
• 1 teaspoon smoked paprika (optional)
• 1 tablespoon tomato puree
• 1 x 227g tin chopped tomatoes
• 100ml reduced-salt chicken stock
• Freshly ground black pepper
• 4 basil leaves, roughly chopped