Easy falafel burgers

Name: Easy falafel burgers
Prep time: 10 min
Cook time: 10 min
Total time: 20 min
Cuisine: Middle Eastern
Ingredients: 250g chickpeas from a can; 1 medium onion, finely chopped; 2 garlic cloves, crushed; 2 tsp ground coriander; 2 tsp ground cumin; small pack flat-leaf parsley, chopped; 2 rounded tbsp plain flour; 2 tbsp vegetable oil; 100g hummus; 4 burger buns, cut in half; watercress, to serve