Mix the breadcrumbs, chilli powder,
cumin, crushed chillies, if using, and lime
zest with ½ tsp salt and lots of black
pepper. Spread over a plate. Toss the
prawns in the flour, then dip them into
the egg and then into the crumbs. Shake
off excess crumbs. Can be chilled in one
layer for up to one day ahead.
When ready to cook, heat a few
centimetres of oil in a large, deep frying
pan. The oil is hot enough when a few
crumbs tipped into it sizzle and turn
brown. Fry the prawns in batches for
2 mins, turning halfway, until the crumbs
are crisp and golden all over. Lift them
onto kitchen paper to drain (they will
keep in a low oven for 15 mins if
necessary), then serve on a warm plate,
with lime wedges scattered around.
Mix the lime juice and coriander into the
mayonnaise and serve alongside.