Lamb burgers with tzatziki

Name: Lamb burgers with tzatziki
Prep time: 40 min
Cook time: 25 min
Total time: 1 h 5 min
Cuisine: European, Mediterranean, Greek
Ingredients: 1kg lamb mince; 1 onion, finely chopped; 2 garlic cloves, finely chopped; 2 tsp ground cumin; 1 tsp ground coriander; 1/4 tsp ground cinnamon; 1/2 tsp ground allspice; 1/2 tsp dried chilli flakes; 2 tbsp chopped flat-leaf parsley; 1 egg; 6 sourdough rolls, split; 2 roasted capsicums, cut into strips; 1 cup (280g) thick Greek-style yoghurt; 1 Lebanese cucumber, grated; 2 garlic cloves, grated; 2 tbsp chopped mint, plus extra leaves to garnish