In a medium skillet combine broth, zucchini, crookneck, onion, garlic and mushrooms and cook covered until tender about 6-7 minutes. Drain if necessary.
2In a medium bowl, whisk together eggs, cream, basil, parsley, salt, pepper and mozzarella cheese.
Divide vegetables evenly among 8 lightly sprayed or oiled gratin dishes. Pour in egg mixture, filling each gratin about 3/4 full.
3Transfer to to oven and bake until eggs are set, 20 to 25 minutes.
While baking saute 1/2 cup onion in olive oil until tender but not brown.
When eggs are set remove from oven and sprinkle with feta cheese, sauteed onions, freshly ground black pepper and drizzle with additional olive oil and Greek seasoning. Let set 5 minutes before serving.
Frittata may be baked in a single dish. I use my 12 inch cast iron skillet when I make a single frittata.
I have substituted fresh steamed spinach for the zucchini and yellow squash and added halved grape tomatoes. I use whatever I have on hand from the garden or go by my mood at the moment. The topping is what makes this frittata so special.