Ingredients

2 small fennel bulbs
1 yellow onion, thinly sliced
2 tablespoons good olive oil
1 tablespoon unsalted butter
2 pounds russet potatoes (4 large potatoes)
2 cups plus 2 tablespoons heavy cream
2 1/2 cups grated Gruyère cheese (1/2 pound)
1 teaspoon kosher salt
1/2 teaspoon freshly ground black pepper

Instructions

Preheat the oven
to 350 degrees F.

Butter the inside of a 10-by-15-by-2-inch (10-cup) baking dish.

Remove the stalks from the fennel and cut the bulbs in half lengthwise. Remove the cores
and thinly slice the bulbs crosswise, making approximately 4 cups of sliced fennel. Saute
the fennel and onions in the olive oil and butter on medium-low heat for 15 minutes, until
tender.

Peel the potatoes, then thinly slice them by hand or with a mandoline. Mix the sliced
potatoes in a large bowl with 2 cups of cream, 2 cups of Gruyère, salt, and pepper.
Add the sauteed fennel and onion and mix well.

Pour the potatoes into the baking dish. Press down to smooth the potatoes. Combine the
remaining 2 tablespoons of cream and 1/2 cup of Gruyère and sprinkle on the top.
Bake for 1 1/2 hours, until the potatoes are very tender and the top is browned and
bubbly. Allow to set for 10 minutes and serve.