Season steak with Creole seasoning. Grill on an oiled rack set five or six inches atop a hot gas grill or charcoal, about three minutes per side for medium-rare. (Alternatively, grill steaks in a hot well-seasoned ridged pan over moderately high heat.) Transfer steak to a cutting board; let stand five minutes. Cut steak into thick slices with a sharp knife at a 45-degree angle.

Spoon vinaigrette generously onto four large plates; divide greens evenly atop. Arrange steak slices on greens.

Vinaigrette:

Add vinegar, mustard, and jelly to a medium bowl; whisk to combine. Add oil in droplets, whisking constantly, until fully incorporated and emulsified. Season with salt and pepper. Makes about 1 cup.