Melt 3 tablespoons of the butter over medium heat in a large skillet and add the garlic and ginger. Sauté until fragrant, 1 minute, then sprinkle with the flour. Combine well and continue cooking, stirring constantly, until the mixture is smooth and light gold in color, about 2 minutes longer.
Add the cream and sugar and cook, stirring constantly, until the mixture is smooth and the sugar has dissolved. Slowly stir in the lime juice and season to taste with salt and pepper.
Continue cooking until the sauce thickens to a rich, creamy consistency, 3 to 4 minutes more, then stir in the scallions and half of the chopped cilantro. Transfer the sauce to a bowl and cover to keep warm.
Wipe out the pan, return it to the stove and add the remaining tablespoon of butter along with the vegetable oil.
Turn the heat to medium-high and once hot, add the scallops in a single layer.
Note: The scallops need about 3/4-inch of space between them in order to sear properly. If the pan seems overcrowded, cook them in 2 batches.
Sear the scallops until they develop a golden crust on the outside, 1-1/2 minutes per side (see notes).
To serve, spoon a portion of sauce onto individual serving plates, top with scallops and garnish with the remaining chopped cilantro.
Tips for Making This Recipe
About the Scallops:
For best results, choose "dry" sea scallops - 16 to 20 per pound size. Depending on their size, plan on 5 to 6 scallops for each serving.The word "dry," when referring to scallops, means that they have not been soaked in the brine-like solution often used to help prevent them from losing their natural moisture. If not clearly marked, ask your fishmonger if the scallops you're buying are "wet" or "dry." Use only the "dry" variety in this recipe as you will not be able to sear the "wet" type properly.Be sure that you work quickly with the scallops and don't overcook them. When cooked in a moderately hot pan, a minute-and-a-half per side should do it. You are looking for a little bit of a crust around the edges and a creamy colored, slightly translucent center.