Boneless loin of pork stuffed with dried plums (also known as prunes) is a classic European combination. Here we use readily available boneless pork tenderloins, add a flavorful and moist stuffing, then finish the meat with a luscious sage-scented cream sauce.
Even if you don't have the time or inclination to make the sauce, this pork is also delicious unadorned.
To make the stuffing, melt the butter in a large skillet and cook the onion, celery, fennel, and orange zest over medium heat until soft, about 8 minutes. Place the bread crumbs in a large bowl. Add the sautéed onion mixture to the bowl and stir in the dried plums and sage, then salt and pepper to taste.
Position a rack in the middle of the oven and preheat the oven to 400 degrees F.
Prepare the pork tenderloins by cutting each fillet lengthwise to open (split) the meat in half; don't cut all the way through and leave one inch at either end intact. Lightly flatten the center of each piece of pork with the smooth surface of a meat mallet or with a rolling pin. You need to widen the center opening so there's room to insert the stuffing.
Divide the stuffing between the tenderloins and pinch the edges of the pork together to cover the stuffing.
Transfer the meat to an oiled baking pan, split side down. Brush the top and sides of the meat with the melted butter and season with salt, pepper, and ground fennel. Roast until the meat is cooked through, 25 to 35 minutes (it should reach 155 degrees F on an instant-read meat thermometer). Remove the pork from the oven and let it rest for 5 minutes before slicing.
While the meat is roasting, make the sauce. Melt the butter in a small saucepan and add the shallots. Cook over medium heat until soft, about 5 minutes. Add the brandy, if using, and cook until the liquid is almost evaporated. Add the sage, dried plums, and cream. Cook slowly until the sauce thickens, 10 to 15 minutes. Add the pan juices from the pork to the sauce, and season to taste with salt and pepper.
To serve, slice the pork into 1-1/2-inch-thick slices and nap with some of the sauce. Serve hot.