In a bowl, mix the butter, coriander, chilli and lime zest with a little seasoning.
Gently lift the green husks back from the corn and remove the silky fibres. Put the husks back in place and wrap each cob tightly in foil. If the corn is huskless, simply wrap each cob in a double layer of foil.
Cook under a medium grill for 20 minutes, turning for even cooking. To barbecue, cook over white–hot coals for about 20 minutes.
To serve, carefully remove the foil, leaving some of the husk to hold the cobs with, and top with a spoonful of the coriander butter and a squeeze of lime.