Seared with a pat of butter in a hot skillet, the steak is presented with potent Dijon mustard and our Bistro Pommes Frites.
Heat a 14-inch skillet over high heat until very hot. Season steaks on both sides with salt and pepper. Add 1 teaspoon butter to one area of skillet, and immediately place a steak on top. Repeat with remaining butter and steaks. Cook steaks, without moving them, 3 minutes. Flip steaks, and cook until an instant-read thermometer inserted into the thickest part registers 125 degrees to 130 degrees (for medium-rare), 2 to 3 minutes more.
Transfer steaks to warmed plates, and let rest 5 to 10 minutes. Serve with mustard and steak sauce if desired.