Heat the oven to 400 degrees.
Whisk together the eggs and heavy whipping cream in a mixing bowl. Season with salt and pepper to taste.
Blend together the crust ingredients, and press into a well greased quiche pan.
Heat the olive oil in a skillet over medium heat.
Stir in the onions, and saute until softened.
Mix in the garlic, and saute for another 30 seconds.
Add in the spinach, and saute until wilted.
Let the spinach mixture cool slightly, and then spread over the crust.
Sprinkle with the feta cheese.
Pour the egg mixture over the top.
Cover loosely with foil, and bake for 20 minutes.
Reduce the heat to 350, remove the foil and sprinkle with the mozzarella cheese.
Bake for another 20-25 minutes, or until the crust is browned and the filling is cooked through.