In a large pot of boiling water, cook the rutabaga until it’s very tender. Drain and mash in the pot with a potato masher, adding the butter and some salt and pepper. Set aside to cool slightly, and preheat the oven to 350F.
Add the eggs to the rutabaga and mix them together well. In a small bowl, stir together the flour, brown sugar, baking powder and nutmeg; stir into the rutabaga. Scrape into a shallow baking dish, smoothing the top. Stir together the crumbs and butter and sprinkle overtop.
Bake for 25-30 minutes, until slightly puffed and golden. Serves 6-8.