Preheat the oven to 375°F (191°C).

Whisk together eggs, milk, salt, and pepper in a bowl, then mix in 3/4 cup of cheese (cheddar for Garden Vegetable or feta for Mediterranean).

Heat olive oil in an oven-safe skillet over medium heat. Add garlic and cook for 30-60 seconds, being careful not to brown it.

For the Garden Vegetable version, add red onion and sweet potato, cooking for 5 minutes until softened. Add zucchini and red peppers, seasoning with salt and pepper. Cook for another 5 minutes.

Pour the egg mixture over the vegetables and cook for 5 minutes without stirring, until it begins to set around the edges. Sprinkle the remaining cheese on top.

For the Mediterranean version, mix spinach, tomatoes, artichokes, and prosciutto into the egg mixture before pouring it into the pan.

Transfer the skillet to the oven and bake for 22–26 minutes, until the frittata is puffy and the center is no longer wet.

Let the frittata cool for 10 minutes before slicing and serving. Optionally top with chopped fresh parsley.