2½ lbs Yukon Gold Potatoes, peeled and thinly sliced, kept in a bowl of water until you are ready to use them to prevent browning
1 tablespoon Olive Oil
1 Onion, thinly sliced
Half a Fennel Bulb, core removed, thinly sliced
1 tablespoon Butter
2 cups Heavy Cream
1 tablespoon fresh Thyme
¼ teaspoon grated Nutmeg
Coarse Salt & freshly ground Pepper
Preheat oven to 375 degrees. Heat cream, and 1 1/2 teaspoons salt in a medium saucepan over medium heat until bubbles form around edge. Season with nutmeg and pepper. Remove from heat.
In a large skillet, warm olive oil over low heat, then saute onion and fennel for about 15 minutes.
Butter a baking dish. Transfer potatoes to the buttered dish. Scatter onion and fennel slices in with potato. Layer the potato and the onion/fennel mixture, alternating one and then the other, with a little thyme in each layer, until all potatoes, onions, and fennel. are used up. Pour the warm cream mixture over top. Gently push potatoes down, and continue to pour the cream mixture over top. Bake (with a baking sheet placed on the rack below to catch drips) until potatoes are fork tender and top is bubbling and brown, about 1 hour and 15 minutes.