Preheat oven to 475°F with racks in upper and lower thirds, with a sheet pan in lower third.
Toss fries with 2 tablespoons melted schmaltz in a hot sheet pan, then bake according to package instructions until golden and crisp.
Meanwhile, pat steaks dry, then rub with peppercorns and 1/2 teaspoon salt.
Heat remaining tablespoon schmaltz in an ovenproof 12-inch heavy skillet over medium-high heat until it shimmers. Sear steaks on all sides, about 3 minutes total. Transfer skillet to the upper third of oven and roast 5 to 10 minutes for medium-rare. Transfer steaks to a plate and let rest 5 minutes.
Add wine to skillet and boil, scraping up brown bits, until reduced by half, about 1 minute. Add water and meat juices from resting plate and boil briskly until reduced by half, 3 to 4 minutes. Whisk in 2 tablespoons schmaltz until incorporated. Season with salt and pepper.
Sprinkle fries with tarragon. Serve steaks with sauce and fries.