Mexican Bean Soup

• 700 g passata (tomato cooking sauce)
• 840 g corn kernels, tinned
• 840 g black beans, tinned, drained rinsed
• 2 tbsp Mexican or fajita spice mix
• 1 l vegetarian stock, salt reduced
• 0.5 cup coriander/cilantro, to serve (optional)
• 0.5 cup Plain Greek yoghurt, to serve (optional