Peel the papery layers from the garlic cloves by pressing the cloves with the side of your knife until you feel the layers release. Then, peel off the papery layers and slice the garlic into small pieces.
Prepare the meat by removing the excess fat and membrane from the skirt steak with a knife.
Pat dry and season both sides with salt and pepper.
In a large skillet (I like using a cast iron skillet if you have one), heat oil over medium-high heat.
Add skirt steak tot he skillet. Sear for about 3 minutes on one side, flip, and sear for 3 minutes on the other side.
Remove steak from skillet, place it on a cutting board or plate, and let it rest.
In another skillet, melt butter over low heat. Add garlic and cook until it's lightly golden. Approximately 3 minutes.
Slice the steak across the grain into thin pieces. This will be the first time you'll see the steak's doneness.
If you're not happy with the steak's doneness, you can put the steak back into the skillet for a few more minutes but be very careful if you decide to do so. Skirt steak is best served medium or medium rare, and it's easy to overcook since it's a thin cut of beef.
If you're happy with the steak's doneness, place the sliced steak on a plate and spoon the garlic butter over the steak. Sprinkle with parsley.