Combine the cumin, garlic salt, oregano and mustard powder in a small bowl. Sprinkle the pork medallions on all sides with salt, followed by the rub.
In a large straight-sided saute pan, heat the canola over high heat until it begins to smoke, then turn down the to medium. Add the pork medallions and sear until caramelized on one side, 3 to 4 minutes. Flip, then sear on the other side until the pork reaches an internal temperature of 130 degrees F, about 4 more minutes. Remove the pork and set aside to rest. Return the pan to the heat and add the scallions and garlic. Cook over low heat until softened, about 3 minutes. Add the turnips and cook, stirring to coat the vegetables, for 1 minute. Add the white wine and chicken stock, scraping up any brown bits on the bottom of the pan. Bring to a simmer over medium heat and reduce by three-quarters, about 5 minutes. Chiffonade 1/2 cup of the turnip greens and add to the sauce with the butter and rosemary. Return the pork and any accumulated juices to the pan. Remove from the heat and top with the Parmesan. Divide among plates and garnish with the chives.