Potato, Turnip, and Caramelized Onion Gratin

Alright, here's another recipe in my series of notes from the Vegetarian Thanksgiving Class I took at the Chopping Block. I heard that this recipe was really good, but unfortunately I wasn't able to taste test it. At the time, I was in the middle of my Protest of Deliciousness (i.e. no cheese) AND I'm lactose intolerant, so there was no way I was going to risk eating any of it! Nevertheless, I give you the recipe--along with my notes--in case you want to make it for yourself. The friend who I took the cooking class with really enjoyed it, so I hope you do too!!

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Potato, Turnip, and Caramelized Onion Gratin
For the caramelized onions:
2 tablespoons extra virgin olive oil
2 tablespoons butter
2 red onions, sliced thin
1/2 cup sherry wine
salt and pepper to taste.

Heat a sauté pan over medium heat and add the olive oil and butter. Sauté the onions until they are nicely caramelized, stirring occasionally, about 20 minutes. If browned bits of fond build up on the bottom of the pan while caramelizing, deglaze with a touch of water. Once the onions are caramelized, add the sherry and reduce until dry. Season to taste with salt and pepper.

2 russet potatoes, peeled and thinly sliced
3 turnips, peeled and thinly sliced
1 cup whole milk
1 cup heavy cream
1 tablespoon thyme, roughly chopped
Freshly grated nutmeg to taste
Salt and pepper to taste
2 cups Gruyere cheese, grated

Preheat oven to 375 degrees and butter a baking dish.
Heat together the cream, milk, and thyme until steaming. Allow this mixture to steep for 10 minutes.

Place one layer of sliced potatoes, slightly overlapping, in the baking dish to cover the bottom. Season the potatoes with salt, pepper, and nutmeg to taste. Spread a thin layer of the caramelized onions over the potatoes and ladle just enough milk/cream mixture to barely cover the onions. Sprinkle with a little cheese. Repeat this process with the turnips and continue alternating until all of the potatoes, turnips, and onions are used up.

Top the gratin with more cheese and bake, covered with foil, until potatoes are tender and top is golden, about 1-1.5 hours. Allow to sit for 10 minutes before serving.

Notes from class:
* Gratin - a baked casserole with liquid and cheese
* Onions - mostly water. Cooking them releases steam/water, concentrating the flavor.
* Nutmeg - the seed of an evergreen tree
* Thyme - has woody stems that you don't want in your food
     * To use: just pull off leaves and discard woody stems
* Caramelized onions:
     * Get pan hot first before adding olive oil.
     * Once olive oil is hot, then add the onions.
     * Add salt right away to the onions to get the flavor to stay.
     * Wait until onions are halfway cooked before adding butter.
* Deglaze - pulling the color off the bottom of the pan by adding liquid.
* When covering gratin, make sure to tent the aluminum foil.
     * If it's too tight, the cheese will melt and stick to the foil.