Directions

• Preheat the oven to 425 °F. In a large bowl, whisk together the eggs, milk, garlic, ¼ teaspoon of the salt and about 2 pinches of freshly ground black pepper until well blended. Whisk in half of the cheddar cheese, reserving the other half for later.
• In a 10-inch, well-seasoned cast iron skillet or oven-safe sauté pan, warm the olive oil over medium heat. Add the onion and the remaining ¼ teaspoon salt. Cook, stirring frequently, until the onion is tender and translucent, about 3 to 5 minutes.
• Add the broccoli and water to the pan, then cover and steam the mixture until the broccoli is brighter green and easily pierced by a fork, about 2 to 3 minutes. Uncover, and add the spinach and green onions. Cook, stirring constantly, until the spinach has wilted, about 30 to 60 seconds.
• Arrange the mixture in an even layer across the skillet. Whisk the egg mixture one last time and pour it into the pan. Sprinkle the frittata with the remaining cheese. Put the pan in the oven and bake until you can shimmy the pan and see that the middle is just barely set, about 12 to 15 minutes.
• Once the frittata is done baking, let it rest for 5 to 10 minutes before slicing. Serve immediately.