Chickpea and cauliflower-stuffed mushrooms

Ingredients

• 8 medium flat mushrooms
• 2 tablespoon olive oil
• 1 onion, finely chopped
• 2 clove garlic, finely chopped
• 2 teaspoon coriander seeds, crushed
• 1 teaspoon caster sugar
• 1/2 head cauliflower, cut into small florets
• 400 gram can chickpeas, rinsed, drained
• 1 tablespoon harissa paste
• 400 gram can cherry tomatoes
• 100 gram baby spinach leaves
• greek-style yoghurt, coriander leaves to serve