Preheat oven to 375°F / 190°C. Grease an 8-inch square baking dish with oil or butter.
Peel the turnips and cut into small cubes.
Place the turnips into a pot of water, bring to the boil then reduce the heat and simmer for 10 minutes or until tender. Drain well.
Add the cooked turnips to a mixing bowl with the diced apple, and toss with the flour and baking powder.
Stir in the lightly beaten eggs, melted butter, sugar, salt, pepper and nutmeg. Toss to combine, then pour into the prepared baking dish.
In a small bowl, whisk the topping ingredients together, then sprinkle over the turnip mixture.
Bake, uncovered, for 25-30 minutes or until risen and cooked.
Serve and enjoy!
Notes
Ensure that the turnips and apples are all cut roughly the same size. This helps them cook evenly.For the best flavor, use sweet, eating apples, like Honeycrisp or gala.If you don't have plain bread crumbs, you can use panko breadcrumbs or even cracker crumbs.If the top looks like it is getting too browned, you can add a layer of foil to the top for the remainder of the cooking time.You can also make this urnip casserole in a slow cooker. Simply assemble the ingredients in the pot, set it on low, and cook for four hours or until the turnips are tender.