Preheat oven to 450°F. Place a rimmed baking sheet in oven (do not remove pan while oven preheats).
Heat 1 1/2 tablespoons oil in a large skillet over high. Sprinkle fillets with 1 1/4 teaspoons salt and 1 1/4 teaspoons pepper. Cook fillets in hot oil, turning occasionally, until browned on all sides, 6 to 8 minutes.
Transfer fillets to hot baking sheet. Do not wipe skillet clean. Roast fillets at 450°F on bottom rack until a thermometer inserted in thickest portion registers 120°F to 125°F for medium-rare, about 10 minutes. Remove from oven; let stand 5 minutes.
Add shallot and thyme to skillet. Cook over medium-high, stirring often, until lightly browned, 1 to 2 minutes. Add wine. Bring to a boil; simmer until reduced by half, 2 to 3 minutes. Add stock, and bring to a boil; boil, stirring occasionally, until slightly syrupy and reduced to 2/3 cup, about 15 minutes. Remove from heat. Stir in butter, parsley, mustard, remaining 1 1/2 tablespoons oil, remaining 1/4 teaspoon salt, and remaining 1/4 teaspoon pepper; stir until butter melts.
Thinly slice beef; serve with sauce.