Heat olive oil and butter in a frying pan until it begins to bubble. Add garlic and fry for 30 seconds over a medium heat. Add prawns and fry for 1 or 1 ½ minutes each side (depending on size). Squeeze half a lemon into the pan and mix into the cooking juices. Remove from pan and drizzle with cooking juices.
Serve with salad leaves, lemon wedges and crusty bread.