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. (We like to leave some husks on because as they burn they give the corn added smoky flavours.)
Remove any 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 each corn cob is completely char-grilled. It should take around 15 minutes depending on your heat.
Once your corn is char-grilled on all sides, pull the husks right back and arrange them on a serving plate or tray. (For 4 people, keep whole; for more people, chop in half.)
Generously slather butter on each corn cob, then generous spreads of mayonnaise, and squeeze juice of one lime onto all cobs.
Sprinkle ancho chilli powder, (optional) dried chilli flakes, crumbled cotija cheese, (optional) Parmesan cheese, and fresh coriander onto the corn cobs.
If you’re entertaining, garnish the tray of corn cobs with additional lime quarters or slices, and if your guests like spice, optional birds-eye chillies.
Serve additional dishes of ancho chilli powder/chilli flakes and limes on the side so guests can sprinkle and squeeze as they like.