Combine the mayonnaise and peanut rayu to create a rayu mayonnaise.
In a second bowl, to make the pickled cucumbers, combine the rice vinegar, water, caster sugar, sesame oil and seeds.
Stir with a whisk until the sugar is dissolved and add the sliced cucumber and leave to marinate for 20-30 minutes in the cold liquid.
Drizzle some oil on the pre-heated barbeque ridge or griddle pan and add the burgers.
Over indirect heat or medium/low heat, cook the burgers on both sides for 4-5 minutes each side until cooked through.
Once the burgers are cooked, drizzle the burger buns with olive oil and warm on the barbecue. When warmed, remove from the barbecue and place on a serving platter.
Assemble the burgers on brioche buns with rayu mayonnaise, pickled cucumber, crispy onions and kimchi.