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 your lime butter and lemon mayonnaise.
To make the lime butter, add the softened butter, juice of 1 lime, fish sauce, and chopped fresh coriander to a bowl and combine well, stirring vigorously with a wooden spoon until all ingredients are well combined. Scoop into a serving dish and return to the fridge so it doesn’t melt.
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, place them on a serving plate or tray. Squeeze juice of one lime onto all cobs, and lightly sprinkle sesame seeds, dried chilli flakes and fresh coriander onto the cobs. Add additional lime quarters to the tray.
Serve with the dishes of lime butter and lemongrass mayonnaise.