Mexican chicken stew

INGREDIENTS

• 1 tbsp vegetable oil
• 1 medium onion , finely chopped
• 3 garlic cloves , finely chopped
• ½ tsp dark brown sugar
• 1 tsp chipotle paste (we used Discovery)
• 400g can chopped tomatoes
• 4 skinless, boneless chicken breasts
• 1 small red onion , sliced into rings
• a few coriander leaves
• corn tortillas , or rice to serve