Bulgogi burgers with quick-pickled cucumbers

Name: Bulgogi burgers with quick-pickled cucumbers
Cook time: 30 min
Total time: 30 min
Cuisine: Asian, Korean
Ingredients: rice vinegar 200ml; caster sugar 75g; ground turmeric 1 tsp; Lebanese cucumber 1 or 1 medium cucumber, thinly sliced; sunflower or vegetable oil 4 tsp; brioche buns or soft white burger buns 4; mayonnaise 5 tbsp; toasted sesame oil 1 tsp; white cabbage ½ small, cored and finely shredded; soft light brown sugar 2 tsp; light soy sauce 4 tsp; beef mince 500g; soft breadcrumbs 50g; garlic 2 cloves, crushed; ginger grated to make 2 tsp; gochujang 2 tbsp, plus extra for serving (optional); toasted sesame seeds 2 tbsp; black peppercorns a generous grinding