How to Make It
Preheat the oven to 375°. In a large skillet, heat the olive oil. Add the shallots and garlic and cook over moderate heat until softened, about 3 minutes. Add the spinach in batches and cook, turning it with tongs, until wilted, about 5 minutes. Season with 1/2 teaspoon salt and the crushed red pepper. Spread the spinach in a greased 9-inch pie plate or casserole in an even layer.
Meanwhile, in a medium bowl, whisk the eggs with the milk and the remaining 1/2 teaspoon salt until light yellow. Stir in the mozzarella.
Pour the egg mixture over the spinach and sprinkle the Parmesan cheese on top. Bake the quiche for about 25 minutes, until the center is firm to the touch. Remove from the oven and let cool for 10 minutes before cutting into wedges and serving.