Adam Liaw’s grilled chicken ranch burger

Ingredients4 chicken thigh filletssalt and black pepper, to season2 tbsp olive oil4 burger buns1 tbsp melted butter¼ head iceberg lettuce, shredded and soaked in iced water1 red onion, halved, very thinly sliced and soaking in iced water1 avocado, thinly slicedRanch burger sauce½ cup sour cream½ cup mayonnaise1 tsp Dijon mustard1 tbsp finely chopped chives1 tbsp finely chopped dill1 tbsp finely chopped parsley1 medium dill pickle, finely chopped½ tsp sugarjuice and grated zest of ½ lemonMethodStep 1Cut deep slits all over the chicken fillets so that they flatten out a little, then give them a little bash with the flat of your knife. Season the chicken very well with salt and pepper, add the oil, mix and refrigerate for at least 1 hour.Step 2Heat a grill pan over medium heat and grill the chicken, turning once or twice, for about 6 minutes until well browned and cooked through.Step 3For the ranch burger sauce, combine all the ingredients and mix well.Step 4Cut the buns in half if necessary, then toast and brush with a little melted butter. Spread the top and bottom slices generously with the sauce, add a piece of chicken, and top with the lettuce, onion and avocado.