Caramelised red onion smashburgers with buttermilk mash, cheddar, pickles and greens

200g 5% beef mince

2 tsp olive oil

1/2 red onion

1 clove of garlic

1 tbsp balsamic vinegar

1/2 tsp sugar

1 tsp reduced fat hummus

1/2 tsp Dijon mustard