Gruyere Fennel Potatoes

3 small fennel bulbs
1 large yellow onion, sliced
3 Tablespoons olive oil
1 Tablespoon butter
4 pounds Russet potatoes
5 cups of heavy cream
1 pound of Gruyere cheese
salt and pepper

Remove stalks and core from fennel bulb. Thinly slice the fennel and onions and saute in the olive oil and butter over medium-low heat for 15 minutes.

Peel the potatoes and thinly slice. Mix the sliced potatoes in a bowl with cream, cheese, salt and pepper. Add the sauteed onion and fennel.

Pour the potatoes into a buttered baking dish.
Bake at 350 degrees for 1 1/2 hours or until potatoes are tender.