1. For the Steaks: Heat oil in 12-inch heavy-bottomed skillet over medium-high heat until smoking. Meanwhile, pat steaks dry with paper towels and season both sides with salt and pepper. Lay steaks in pan, leaving 1/4 inch between them. Cook, not moving steaks, until well browned, about 4 minutes. Using tongs, flip steaks and continue to cook until instant-read thermometer inserted in center registers 120°F for rare to medium-rare, 3 to 7 minutes. Remove steaks to platter and tent loosely with foil while preparing herb sauce.

2. For the Port Sauce: Return now-empty skillet to medium-low heat; add shallot and cook, stirring constantly, until lightly browned, about 2 minutes. Add wine and bring to simmer, scraping bottom of pan with wooden spoon to loosen browned bits. Add 1/4 cup Sauce Base, vinegar, and any accumulated juices from steak; return to simmer and cook until slightly reduced, about 1 minute. Off heat, whisk in fresh thyme, and butter; season with salt and pepper to taste. Spoon sauce over steaks and serve immediately.