You could certainly use the spinach fresh but, out of my experience, I'd just wash it and place it in a bowl, pour some boiling water over just to wilt it a little so it gets easier to handle.
In a glass bowl mix the eggs, egg whites, pepper, the milk, half of the cheese and the wilted spinach, the cheese/creme fraîche.
Cut the bacon into half lengthwise so it becomes long strips. Trim some of the fat off if you prefer.
In a silicone muffin tray place on the edge a bacon strip (thinner if the bacon has not been de-salted). Pour in (half full) the egg mixture. Sprinkle few sunflower seeds and some more grated mozzarella cheese on top and place in the oven.
Bake for 20-25 minutes at 200°C or 400F.
When ready, take out and serve pretty immediately but served cold are also delicious.