Preheat your oven to 425°F. While it heats, mince the garlic cloves, dice the onion into 1/4-inch pieces, cut the broccoli into bite-sized 1/2-inch florets, and chop the green onions. Having everything prepped and ready will keep the cooking process moving smoothly without scrambling mid-recipe.

In a bowl, whisk together the eggs, milk, minced garlic, salt, black pepper, and 3/4 cup of cheddar until well combined and smooth. This mixture will be the foundation of your frittata, so make sure the cheese is evenly distributed. Set aside while you work on the vegetables.

Heat the olive oil in a 10-inch oven-safe skillet over medium heat. Add the diced onion with 1/4 tsp salt and cook for 3-5 minutes, stirring occasionally, until softened and slightly translucent. Add the broccoli florets and 1/3 cup water, then cover the skillet and let it steam for 2-3 minutes until the broccoli is just tender-crisp. I like to keep the broccoli with a little crunch so it doesn't get mushy when baked.

Uncover the skillet and stir in the spinach and green onions, cooking for 30-60 seconds until the spinach just wilts. Spread the vegetable mixture evenly across the skillet, then slowly pour the egg custard from Step 2 over the vegetables, making sure it fills the gaps and distributes evenly. Sprinkle the remaining 1/2 cup of cheddar over the top—I always use Tillamook sharp cheddar because it melts beautifully and adds a richer flavor.

Transfer the skillet to the preheated 425°F oven and bake for 12-15 minutes, until the edges are set and the center is just barely jiggly in the middle—the frittata will continue to cook slightly as it cools. The top should be lightly golden and the cheese melted and bubbly.

Remove the frittata from the oven and let it rest for 5-10 minutes before serving. This resting period allows the eggs to continue setting and makes it much easier to slice without falling apart. Serve warm or at room temperature.