The key to garlic prawns is to get everything prepped and ready in advance because, to avoid overcooking your prawns, we are going to use a super-fast, high-heat cooking method. So to prepare, peel the prawns and remove the vein (if not already done). Peel and crush (mince) the garlic. Squeeze the juice from the lemon (you'll want about 3 tablespoons of juice). Chop the parsley - you need about one-third of a cup or ½oz (15g)
Heat the olive oil in a heavy frying pan (skillet) over high heat until it just begins to smoke. As soon as you see a haze of smoke turn the heat down slightly and place the prawns in an even layer on the bottom of the pan and cook for 1 minute without stirring. Season the prawns with salt then cook, stirring, for about 1 minute until they begin to turn pink.
Stir in the garlic and red pepper flakes then cook, stirring, for another 1 minute. Stir in the lemon juice, 1½ teaspoons of cold butter, and half the parsley and stir well. Cook until the butter has melted (about 1 minute), then turn the heat right down to low and stir in the 1½ tablespoons of cold butter. Again, cook and stir until all the butter has melted and the shrimp are pink and opaque (about 1 to 2 minutes). At this point, the butter will have formed a thick sauce.
Remove the prawns with a slotted spoon and transfer to a serving dish. Continue to cook the butter sauce for about 2 minutes (adding water 1 teaspoon at a time if it's too thick). Season with salt to taste.
Serve the prawns topped with the pan sauce and garnished with remaining chopped parsley. Unbelievably delicious, garlic prawns are great served over Boiled Rice or Creamed Potatoes or any plain pasta. They're also great on toast topped with the garlic-parsley-lemon sauce as a snack.