Home-style chicken curry

INGREDIENTS

• 1 large onion
• 6 garlic cloves , roughly chopped
• 50g ginger , roughly chopped
• 4 tbsp vegetable oil
• 2 tsp cumin seeds
• 1 tsp fennel seeds
• 5cm cinnamon stick
• 1 tsp chilli flakes
• 1 tsp garam masala
• 1 tsp turmeric
• 1 tsp caster sugar
• 400g can chopped tomatoes
• 8 chicken thighs , skinned, boneless (about 800g)
• 250ml hot chicken stock
• 2 tbsp chopped coriander