16 SERVINGS
In France, this dish is called oeufs à la tripe. Since there is no tripe anywhere, I can only assume someone once thought the dish looked a bit like tripe. In any event, it tastes heavenly, if you’re partial to mushrooms and caramelized onions, as I am. Because the dish can be prepared completely in advance, it is ideal for entertaining.
2 dozen eggs
8 tablespoons (1 stick) plus 6 tablespoons unsalted butter
3 tablespoons olive oil
1 pound mushrooms, sliced
1¼ teaspoons salt
½ teaspoon freshly ground black pepper
1 teaspoon fresh lemon juice
5 medium onions, sliced
1⁄8 teaspoon saffron threads
2⁄3 cup all-purpose flour
1 quart milk
1⁄8 teaspoon each freshly grated nutmeg, dried thyme, cayenne pepper
2⁄3 cup heavy cream or additional milk
2⁄3 cup shredded Gruyère or imported Swiss cheese
1. Put the eggs in a large saucepan or flameproof casserole. They needn’t be in a single layer, but don’t pile them high either. Add cold water to cover by at least ½ inch. Bring to a boil, reduce the heat, and simmer for 12 minutes. Remove from the heat and let stand for 5 minutes. Pour off the water and fill the pan with cold water. Peel the eggs immediately to avoid a dark ring around the yolk. (The eggs can be cooked and peeled up to 3 days in advance and refrigerated in a bowl of cold water.)
2. In a large skillet, melt 2 tablespoons of the butter in 1 tablespoon of the oil over moderately high heat. Add the mushrooms and sauté, tossing frequently, until lightly browned, about 10 minutes. Season with ¼ teaspoon of the salt, ¼ teaspoon of the black pepper, and the lemon juice. Set aside.
3. In a large heavy saucepan or flameproof casserole, melt 1 stick of the butter in the remaining 2 tablespoons olive oil over moderately low heat. Add the onions, cover, and cook slowly for 5 minutes. Uncover, increase the heat to moderate, and cook, stirring occasionally, until deep golden brown, about 30 minutes.
4. Crumble the saffron over the onions. Add the flour and cook, stirring, for 2 minutes. Gradually whisk in the milk. Bring to a boil and cook, whisking, for 1 to 2 minutes, until thickened. Reduce the heat to a simmer and cook, stirring frequently, for 3 minutes. Season with the nutmeg, thyme, cayenne, and the remaining 1 teaspoon salt and ¼ teaspoon black pepper. Thin the sauce with the cream. Remove from the heat and set aside.
5. Use 2 tablespoons of the remaining butter to grease 2 large gratin or shallow baking dishes (or use a single dish if you have one large enough). Slice the eggs. Spread a thin layer of the onion-cream sauce over the bottom of each dish. Cover with a layer of half the egg slices, overlapping as necessary. Season the eggs lightly with additional salt and freshly ground pepper to taste. Spoon half the sauce over the eggs and cover with half the sautéed mushrooms. Arrange a layer of the remaining egg slices, season with salt and pepper, and top with the remaining mushrooms and the remaining sauce. Sprinkle the cheese evenly over the top and dot with the remaining 2 tablespoons butter. (The recipe can be completely assembled to this point up to a day ahead. Set aside at room temperature for up to 3 hours or cover and refrigerate overnight.)
6. Preheat the oven to 375°F. Bake the gratins until bubbling hot and lightly browned on top, 15 to 20 minutes. Serve hot.