How to Make It
In a large skillet, melt 3 tablespoons of the butter in the vegetable oil over high heat. When the fat is very hot, dredge the scaloppine one by one in the flour, shake off any excess and add them to the pan without crowding. Brown the scaloppine quickly on both sides, about 1 1/2 minutes; transfer them to a platter.
Add the celery to the pan and turn the heat down to very low. Add the remaining tablespoon of butter, a little salt and all the juices released by the meat. Stir once or twice, cover and cook until the celery is crisp-tender, about 10 minutes.
Add the orange juice and orange zest and increase the heat to moderate. Stir with a wooden spoon to loosen all the cooking residues from the bottom of the pan.
Season the scaloppine with salt and pepper and return them to the pan. Turn them 2 or 3 times in the sauce until heated through. Transfer the scaloppine to a warmed platter. Pour the pan sauce and the celery over the meat and serve at once.