Dice the shallot.

In a skillet, cook the shallots in 8 tbsp of olive oil over medium-high heat, stirring until golden brown, about 4-5 minutes.

Add the vinegar and grapefruit juice and cook over moderate heat until liquid is syrupy and reduced, about 5 minutes.

Add cream, salt, pepper and boil for 1 minute, being careful not to scald the cream.

Reduce heat to low and add a few tablespoons of chilled butter, whisking constantly.

Add remaining butter pieces, a few at a time, whisking constantly and adding new pieces before the previous ones have completely liquefied.

Lift the pan off the heat occasionally to cool down the mixture.

Remove from heat and set aside the beurre blanc sauce.

Pull off and discard any muscle tabs still attached to the scallops.

Pat the scallops dry with paper towels and season with salt and pepper.

In a large, heavy-duty nonstick skillet, heat the remaining 2 tbsp olive oil over medium-high heat.

Add the scallops (in batches if necessary), cook until golden brown on both sides and almost firm to the touch, 2-4 minutes per side.

Add the shallot sauce to the scallops and cook briefly, shaking the pan, until the sauce is reheated.

Serve immediately and sprinkle with chives if using.