Preheat your oven to 350°F (175°C). This ensures that your casserole bakes evenly and comes out perfectly set.
In a skillet over medium heat, spray a little olive oil and add the chopped shallots. Sauté until they become translucent, about 3-4 minutes. Then, add the baby spinach and cook until wilted, stirring occasionally.
In a large mixing bowl, beat the eggs until well combined. Stir in the 2% milk and heavy cream, mixing until smooth.
To the egg mixture, add the crumbled feta cheese, sautéed spinach and shallots, chopped scallions, diced tomatoes, kosher salt, and black pepper. Gently fold the ingredients together until everything is evenly distributed.
Spray your baking dish with olive oil spray to prevent sticking. Pour the egg mixture into the dish, spreading it out evenly.
Place the baking dish in the preheated oven and bake for about 45-55 minutes, or until the casserole is set in the center and lightly golden on top.
Once baked, remove the casserole from the oven and let it cool for a few minutes. Cut into squares and serve warm, garnished with extra scallions if desired.
