Chickpea & coriander burgers

INGREDIENTS

• 400g can chickpeas , drained
• zest 1 lemon , plus juice ½
• 1 tsp ground cumin
• small bunch coriander , chopped
• 1 egg
• 100g fresh breadcrumbs
• 1 medium red onion , ½ diced, ½ sliced
• 1 tbsp olive oil
• 4 small wholemeal buns
• 1 large tomato , sliced, ½ cucumber, sliced and chilli sauce, to serve