In a small bowl stir together the garlic powder, onion powder, basil, thyme, rosemary, cayenne pepper and paprika. Set aside.
Melt the butter in a large frypan over medium heat. Add garlic; cook and stir until fragrant, about 1 minute. Add the prawns and cook for a couple of minutes. Season with the spice mixture and continue to cook and stir for a few minutes. Pour in the beer and Worcestershire sauce; simmer until prawns are cooked through, about 1 more minute. Taste and season with salt before serving.