Melt butter in a sauté pan until it starts to bubble. Add the chopped garlic and cook until it starts to brown (about 1 min) stirring to cook evenly.
Using a small baking pan ( u want the shrimp to lay flat in a single layer and the sauce to cover them at least halfway, I use a loaf pan) pour the rum and olive oil in followed by the butter garlic mix and stir together.
Place shrimp in single layer in pan and let marinate for 10-20 min (if you use frozen shrimp allow them a little longer to dethaw)
turn your oven to broil low temp and place shrimp on rack approximately 6inches from heat source.
Broil shrimp until cooked through (approx 15 min)
remove shrimp from pan and plate, then drizzle a little of the pan sauce over the top.