Shell and devein the prawns while keeping the tail intact.
Pierce a hole through the center of each prawn from top to tail using a skewer.
Sprinkle the prawns with garlic salt.
Thread two thin carrot batons through the hole in each prawn.
Soak the prawns in buttermilk for 30 minutes, stirring occasionally.
Heat the vegetable oil in a deep heavy-based pan.
Sift the flour, polenta, chilli powder, salt, and pepper onto a plate.
Dredge each buttermilk-coated prawn in the flour mixture without shaking off excess.
Deep-fry the prawns in batches for 2 to 4 minutes until golden-brown.
Drain the cooked prawns on kitchen paper.
Mix the mayonnaise and hot chilli sauce in a bowl to create the dipping sauce.
Arrange the prawns around the sauce bowl on a serving plate.