Best-ever Burgers with Spiced Onions

For the burgers:

450g minced beef or lamb, with some fat on it

1 red onion, finely chopped

10g finely chopped root ginger (peeled weight)

2 large garlic cloves, finely grated

¾ tsp garam masala

1 free-range egg

Salt and freshly ground black pepper

6 burger buns or baps

1 large tomato, sliced crossways

For the roasted green chilli yogurt:

3 large green chillies, stalks removed, pierced with the tip of a knife

2 rounded tbsps thick Greek yogurt

2 tbsp crème fraîche or mayonnaise

Good handful of chopped coriander

For the spiced caramelized onions:

1½ tbsp vegetable oil

½ tsp panch phoran spice blend

2 red onions, thinly sliced