Prep the scallops by rinsing under cold water and removing the side connector muscle. Place the scallops on a paper towel-lined baking sheet or plate and pat dry with more paper towels.
Preheat a large skillet over high heat with enough oil to just coat the bottom of the pan.
While the pan heats, season the scallops on all sides with salt and pepper.
When the oil just starts to smoke, carefully place the scallops presentation side down in the skillet and sear for about 2 minutes, or until golden brown.
Turn the scallops to the second side with a fish spatula (or spoon). Reduce the heat to medium-low and add the butter and optional shallot.
Using a spoon, baste the melted butter over the scallops while they finish cooking for about 1 to 1 ½ more minutes. Cook to 115° F internal temperature, which will continue to rise by 10 to 15° as they were cooked in a high heat pan, to a perfect 125° F.
Finish with fresh parsley and a squeeze from half a lemon and immediately remove from the skillet from the stove (to stop the cooking) and serve with the lemon-butter pan sauce.
If you're using frozen scallops, defrost them for 10 minutes in a bowl of water.
Remove connector muscle before cooking as it will become tough.
Olive oil is not recommended for searing scallops as it has a lower smoke point.
The cook time will vary depending on the size of the scallops. Cook to an internal temperature of 115° F, which will rise another 10 to 15° after they are removed from the skillet.
1 pound of scallops can serve 2 to 4 people, depending on the size and how many you serve per person.