Sausage, Egg, and Cheese Casserole with Spinach

Steps

1. 1Heat oven to 325ºF. Place spinach in a large colander and set it in the sink. Grease a 9×13-inch pan lightly with butter or with nonstick spray.
2. 2In a medium skillet over medium-high heat, heat the oil till it shimmers. Cook the sausage till it browns and is nearly cooked through, about 5 minutes. Break it up with a spoon or a spatula as it cooks. Spoon the sausage over the spinach in the colander in the sink. Return the skillet to the stovetop, add a little bit more oil to the pan if necessary, and set it over medium heat. Add the onions. Season with salt. Cook the onions till they begin to caramelize, 7 to 10 minutes. Spoon the onions over the sausage and toss with a spatula or large spoon to gently wilt the spinach. Transfer the spinach-sausage mixture to the prepared pan. Spread the cheese over top.
3. 3Break the eggs into a large bowl, season with 1 to 1.5 teaspoons salt (when I am using Morton’s kosher salt, I use 1 teaspoon; when I use Diamond Crystal, I use 1.5 teaspoons) and fresh cracked pepper to taste. Add the half and half, and beat with a whisk until the mixture is well blended. Pour the eggs into the pan. Season with more pepper to taste. (Note: You can strategically pull leaves of the spinach from the custard so they are at the very top, where they will stay during the baking process — this is purely for visual effect.) Transfer pan to the oven and bake for 25-40 minutes, rotating the pan halfway through. Start checking at 25 minutes, then every 5 minutes thereafter till it’s done — depending on your oven and the material of the pan you are using, it may take more or less time to cook.
4. 4Remove pan from the oven, and let it cool for 5 minutes before serving.