This is my favourite recipe from my favourite food blog, Salt & Fat. Used here with permission from Neven and Jim. Do your tastebuds a favour: visit the original for the full instructions!
Combine all the sauce ingredients in your food processor and chop until they make a coarse, wet mix, no more than 5-10 seconds. Move to a small saucepot and bring to a near boil, then immediately take off heat and let come to room temperature (30-40 minutes).
While you wait, read Jim Ray’s post on grilling burgers. Start your grill and come back into the kitchen to make the rest.
Combine the cilantro and the mayo and refrigerate.
Toss the cucumbers in a small bowl with a few generous pinches of equal parts salt and sugar and let rest until you’re ready to top the burger; yes, this is all it takes to semi-pickle them.
Slice your buns while your hands are still free of meat juices.
In a large and cold glass or metal bowl, combine the meat and the khao man gai sauce. Use your (extremely clean) hands, and don’t overwork the meat. Just handle it enough to fold the sauce in. Shape two dimpled patties. Grill the burgers according to Jim’s method and don’t forget to quickly toast your buns.
To serve, spread cilantro mayo on the bun, top with the burger, then the pickles. Goes great with a beer or a drinking vinegar.