You may choose to adjust or expand this recipe by adding using half celeriac/half potatoes in the dish. The potatoes usually cook much quicker than the celeriac, so make your celeriac slices a little smaller than the potato slices or add the potatoes later.
2 large celeriac bulbs, peeled, sliced into 1/8 inch pieces
2 T. butter
1 T. flour
1 c. chicken or vegetable stock
Salt and pepper to taste
1 c. grated Swiss or cheddar cheese
Simmer celeriac in water over medium heat until tender, about 15 minutes. Drain. In medium saucepan, melt butter, add flour, and cook until golden. Slowly whisk in stock; cook until thickened. Add salt and pepper. Place celeriac in shallow baking dish; top with sauce, sprinkle with cheese, and bake at 375 degrees until golden, about 15 minutes.