Preheat oven to 375°F. In a sauté pan, sauté onions with butter, olive oil and 3/4 of thyme until soft and translucent. Season with salt and pepper. Set aside.
Cover the bottom of a 9×9-in. non-stick pan with a layer of sliced turnips. Top with half of onion mixture, then sprinkle half of cheese overtop, pour half of milk overtop and then add sage. Add a second layer of sliced turnip, then remaining onion mixture, cheese and milk.
Cook, covered, for a half-hour and then uncovered for another half-hour. Garnish with remaining thyme.
Recipe Notes
Per serving: 130 calories, 7 g protein, 7 g fat (4 g saturated fat), 10 g carbohydrates, 2 g fibre, 6 g sugars, 17 mg cholesterol, 253 mg sodium