A delicious shallot sauce with balsamic vinegar and parsley elevates this simple steak dish.
Heat olive oil in a large skillet over high heat. Generously season both sides of shell steaks with coarse salt and ground pepper. Cook steaks until browned, 2 to 3 minutes per side for medium-rare. Transfer to a plate; cover loosely with foil, and set aside.
Reduce heat to medium; add 6 shallots, thinly sliced into rings. Cook, stirring frequently, until softened, 4 to 6 minutes.
Add balsamic vinegar, coarsely chopped fresh parsley, and any accumulated juices from steaks; cook until sauce is just slightly reduced, about 1 minute. To serve, spoon shallot sauce over steaks.