Butternut Squash without sprinkles

3 1/2 pounds butternut squash peeled and cut in 1/4-inch-thick slices (about 6 cups) 1 bunch spinach fresh, washed and stemmed, optional 2 tablespoons butter,[...]

2 cups buttermilk 4 large eggs , separated 2 cups thawed frozen unseasoned, pureed butternut squash 1/3 cup freshly grated parmesan cheese 1 cup stone ground[...]