Tartiflette

4 (about 2 1/4 pounds) Medium russet potatoes, peeled
2 tablespoons plus 1/2 teaspoon Kosher salt, divided
1/2 cup Rendered beef fat or unsalted butter
2 (about 5 cups) Medium yellow onions, thinly sliced
1 1/2 teaspoons Granulated sugar
2/3 cup Dry white wine
1 1/2 teaspoons Fresh sage, thinly sliced
1/2 teaspoon Black pepper, divided
1/4 cup Crème fraîche
1 (1-pound) Fromager d’Affinois round with rind, at room temperature, halved crosswise

Place potatoes in a pot, cover with water, add 2 teaspoons salt and bring to a boil. Reduce heat to medium-low, and simmer about 20 minutes, until potatoes can easily be pierced by a fork. Drain and let potatoes cool. Cut potatoes into 1/4-inch-thick slices and set aside.
Preheat oven to 400°F.
Heat a large skillet over medium-high heat. Add rendered beef fat, or butter, and heat until shimmering, about 2 minutes. Add onions and 1 1/2 teaspoons salt. Cook 10-12 minutes until onions begin to brown.
Add sugar and cook stirring occasionally, until lightly browned, about 8 minutes.
Add 1/3 cup wine. Deglaze the pan by stirring and scraping bottom of skillet, loosening any browned bits, until wine has almost completely evaporated and onions are soft, about 6 minutes.
Add remaining 1/3 cup wine, and cook, until onions are caramelized, 4 to 6 minutes. Then add the sage.
Arrange half of potato slices in an even layer in a 1 1/2-quart oval soufflé dish or 10x 7 x 1 1/2-inch baking dish.
Sprinkle with 1 1/2 teaspoons salt and 1/4 teaspoon pepper. Top with half of the onion mixture (about 1/3 cup). Layer with remaining potatoes, 1 1/2 teaspoons salt and 1/4 teaspoon pepper. Top with onion mixture and drizzle with any drippings in skillet.
Dot casserole with spoonfuls of crème fraîche and arrange Fromager d’Affinois cheese halves on top.
Place soufflé dish on baking sheet, and bake about 20-30 minutes, until it is bubbly and lightly browned.
Serve hot.

Recipe adapted from FoodAndWine.com