Horseradish Parsnip-and-Potato Rosti

Peel and grate potatoes and parsnips; toss with horseradish and salt. Melt 1 tablespoon butter in an 8-inch cast-iron skillet over medium. Press potato mixture into pan. Cook until bottom is golden, 10 minutes. Flip; dot 1 tablespoon butter around edges. Transfer to a 400 degrees oven; bake 25 minutes. Serve, with fried eggs.