Everything worth having in a pan sauce is already stuck to the bottom of the pan when the steak comes out. Those browned bits are concentrated flavour, and leaving them behind is the single most common thing home cooks get wrong about cooking a steak.

The sequence is short and it is not flexible. Pour off the excess fat, add the aromatics, deglaze with the vinegar, then reduce until the sauce coats a spoon. Only then does the cold butter go in, off the heat, one piece at a time.

Marc De Champagne Vinegar does the deglazing here because it is bright enough to cut the fat without the sharpness of a straight wine vinegar. Two tablespoons over a steak is plenty; the sauce is meant to be a finish, not a gravy.