Chickpea & coriander burgers

Name: Chickpea & coriander burgers
Prep time: 15 min
Cook time: 10 min
Total time: 25 min
Cuisine: Mediterranean
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