1. Heat the olive oil in a skillet over medium heat. Add the chopped onion and garlic, sautéing until they are soft and fragrant, about 5 minutes.
2. Add the spinach to the skillet and cook until wilted, about 2-3 minutes. Remove from heat and set aside.
3. In a large bowl, whisk together the eggs, milk, and heavy cream until well combined. Stir in the feta cheese, mozzarella cheese, nutmeg, salt, and pepper.
4. Lightly grease the slow cooker insert with some olive oil. Add the spinach mixture to the slow cooker and spread it out evenly.
5. Pour the egg mixture over the spinach mixture. Gently stir to combine.
6. Cover and cook on low for 3-4 hours, or until the quiche is set and a knife inserted into the center comes out clean.
7. Once done, let it cool slightly before slicing and serving.
Variations & Tips
For a meatier version, add cooked and crumbled bacon or sausage to the mixture. If you have picky eaters at home, substitute the spinach with finely chopped broccoli or bell peppers. For a touch of spice, consider adding a pinch of crushed red pepper flakes or some diced jalapeños. You can also switch out the feta for goat cheese or even sharp cheddar for a different flavor profile. To make it dairy-free, use a plant-based milk and omit the cheeses.
