Moroccan chickpea soup

INGREDIENTS

• 1 tbsp olive oil
• 1 medium onion , chopped
• 2 celery sticks, chopped
• 2 tsp ground cumin
• 600ml hot vegetable stock
• 400g can chopped plum tomatoes with garlic
• 400g can chickpeas , rinsed and drained
• 100g frozen broad beans
• zest and juice ½ lemon
• large handful coriander or parsley and flatbread, to serve