Preheat the Oven: Preheat the oven to 350 degrees Fahrenheit. Liberally grease a 13 x 18-inch half sheet pan with oil (flavorless cooking oil or non-stick spray), ensuring the edges and corners are well-coated to prevent sticking.
Prepare the Egg Mixture: In a large mixing bowl, combine the eggs, half and half, kosher salt, and black pepper. Break the yolks with a fork, then whisk or use electric mixers to blend the ingredients until well combined. Avoid overmixing.
Add Mix-Ins: Stir the diced ham, shredded cheddar cheese, and chopped spinach into the egg mixture.
Pour and Bake: Pour the egg mixture into the prepared baking sheet, spreading it evenly. Bake in the preheated oven for 23 to 27 minutes, or until the eggs are set and no longer jiggly in the center.
Cool and Serve: Allow the eggs to cool for a few minutes before slicing them into 12 squares. Garnish with chopped chives, if desired. Serve as-is, or use for breakfast sandwiches, wraps, or pair with toast, avocado, or fresh fruit.
Notes
Pan Preparation: Eggs can stick to the pan if it’s not greased thoroughly. For best results, use a generous amount of spray oil or line the pan with parchment paper, ensuring it covers the sides and corners.Cheese: Freshly shredded cheese melts better and creates a creamier texture. Avoid pre-shredded cheese, which contains anti-caking agents.Vegetarian Option: Omit the ham for a vegetarian version.Storage: Store individual squares in an airtight container in the refrigerator for 3 to 4 days, or freeze for up to 2 months.