How to Make It
Wrap a slice of bacon around each beef medallion and secure with toothpicks. Season with salt and pepper.
In a large skillet, heat the oil until shimmering. Add the medallions and cook over moderately high heat until richly browned on the bottom, about 2 minutes. Turn the medallions and cook for 1 minute. Add the carrots and onions and cook over moderate heat, shaking the pan, until starting to soften, about 3 minutes. Transfer the medallions to a plate. Add the wine to the skillet and simmer for about 2 minutes. Add the stock, bring to a simmer and return the medallions to the skillet. Simmer the medallions over moderately low heat, turning, until an instant-read thermometer inserted in the center registers 140°, about 3 minutes.
Transfer the medallions to plates. Remove the skillet from the heat and swirl in the butter, 1 tablespoon at a time. Season with salt and pepper and stir in the parsley. Spoon the sauce over the medallions and serve.