Meanwhile, spread peppercorns on a large plate. Season steaks with salt, then press into pepper, coating both sides. In a large skillet, heat 1 tablespoon oil and butter over high. In 2 batches, cook steaks until medium rare, about 8 minutes, flipping once. Let rest on a cutting board, 5 to 10 minutes.

Discard fat from skillet, lightly wipe with a paper towel to remove any loose pepper, and heat over medium. Add wine and cook, stirring and scraping up browned bits with a wooden spoon, until wine is reduced by half, about 2 minutes. Add cream and cook until sauce coats back of spoon, about 4 minutes. Stir in mustard and season with salt.