Remove the outer husks of each corn cob, leaving just 3-4 inner husks on the cob, then carefully peel the remaining husks right back, taking care not to pull them entirely off the cob.
Remove the silky threads from each cob by wiping them off with a damp paper towel.
Soak the corn cobs with remaining husks in a pot of water for 15 minutes.
Heat up your barbecue, griddle or grill pan and add a tablespoon of oil, just enough to cover the surface.
Dry the corn cobs completely with a dry paper towel, then place the corn cobs beside each other on the barbecue, griddle or grill pan. Season the cobs generously with coarse salt.
Grill the corn until its slightly charred, then turn all cobs to char-grill the next side, then once they’re a little charred turn the cobs again until the corn is char-grilled. It should take around 15 minutes. In between turning, make the lemongrass mayonnaise.
To make the lemongrass mayonnaise, add the creamy mayonnaise and lemongrass powder to a bowl, combine well, add to a serving dish, and sprinkle more lemongrass powder (see notes) on top. Return to fridge to keep cool.
Once your corn is char-grilled on all sides, pull them off the stove and transfer to a chopping board to cool down.
After the corn cobs have cooled, cut the kernels off the cobs, slicing from top to bottom as close to the cob, the inner core, as you can.
Slide the corn kernels into a bowl the add the rest of the ingredients: squeeze two limes in, add the fish sauce (if you're not a fan of the funkiness of fish sauce, add half first, then taste, and add the rest little by little), then the dry ingredients, except the lemongrass mayonnaise.
Combine well then transfer the grilled corn salad to a serving dish.
Garnish with fresh coriander sprigs, sprinkle on a pinch of each of chilli flakes, lemongrass powder and sesame seeds, and a teaspoon of toasted sourdough crumbs and croutons.
Evenly distribute some small blobs of lemongrass mayonnaise on top of the salad. Use a teaspoon or if you're a perfectionist, a piping bag.
Pop some lime quarters in the corners of the serving plate or in a separate dish and provide serving spoons and smaller bowls. If you have more leftover lemongrass mayo, you could serve that in a side dish.