Creating the Butternut Squash and Rosemary Frittata can be an enjoyable experience if you follow these simple steps:

1. Preheat the Oven: Preheat your oven to 375°F (190°C). This ensures the frittata cooks evenly.
2. Sauté Vegetables: In an oven-safe skillet, heat the olive oil over medium heat. Add the diced butternut squash and sauté for about 5-7 minutes until slightly softened.
3. Add Aromatics: Stir in the chopped onion and garlic, cooking for an additional 3-4 minutes until the onion becomes translucent and fragrant.
4. Mix Eggs: In a bowl, whisk together the eggs, milk, chopped rosemary, salt, and pepper until well combined.
5. Combine & Cook: Pour the egg mixture over the sautéed squash and onion. Let it cook undisturbed for about 2-3 minutes until the edges start to set.
6. Top with Cheese: If using cheese, sprinkle it evenly on top of the frittata.
7. Bake: Transfer the skillet to the preheated oven and bake for 15-20 minutes, or until the center is set and the top is golden.

Now you have a beautiful Butternut Squash and Rosemary Frittata, ready to impress!