Preheat a large chargrill or barbecue grill on medium. Place bread slices onto a flat surface. Combine oil and garlic in a bowl. Brush garlic oil on both sides of bread. Cook bread slices for 3 minutes each side or until golden and charred.
Combine spring onion, chilli, mango and prawns in a large bowl. Spoon mixture onto chargrilled bread, top with coriander sprigs and serve with lime wedges.