In a medium sized mixing bowl mix the chicken mince, first half of the coriander, chilli, spring onions and fish sauce. If you are making one or two serves you can either repeat this step each night or divide the mixture once mixed.
Heat the oil in a small frypan on low to medium heat. Take a big scoop of the mince mixture (or divide the total mix into quarters) and add to the pan when sizzling. Cook each burger on each side for 5 - 6 minutes each.
Meanwhile add all the salsa ingredients to another medium mixing bowl (again, if you are eating this over a number of nights you might want to make it fresh or have the convenience of making it once). Mix the lime juice through and taste for seasoning.
Wash the four lettuce leaves and when the burgers are done divide them into four pieces and cut each of the four pieces into quarters. Spread evenly across the cos lettuce leaves and top with 1-2 tbsp of salsa. Wrap each cos leaf lengthwise, season with srirarcha if you like and then eat from your hand (over a plate - they can be messy).
