Put the prawns in a bowl with the lemon zest, half the lemon juice, the chilli and coriander. Leave to marinade for 15 minutes.
Meanwhile, rub the garlic clove over the ciabatta slices. Brush 1 tbsp oil over the slices and then griddle each side until golden and set aside.
Heat the remaining oil in a pan and stir-fry the prawns for 5 minutes, until pink and beginning to turn golden. Put into a bowl with the avocado and drizzle over the remaining lemon juice. Place 2 slices of bruschetta on to each serving plate, then top with the prawns and avocado and serve with the rocket leaves.