Preheat oven to 350°.
Gently wipe mushrooms clean. Do not wet or wash them. They'll absorb every bit of that moisture. Pull stems and chop them finely. Gently scoop out the inner black fibers and discard them.
De-thaw spinach and squeeze all the fluids out. You don't want icky runny mushrooms. Feather your dried spinach apart and measure out 1 loose cup.
Add 1 tablespoon oil to pan and add finely chopped onions, garlic and chopped mushroom stems to a heated pan. Fry until translucent but don't burn your garlic. About 3 minutes. Drain on paper towels then add to your cheese mixture.
With the exception of your additional wine and additional half & half - add all ingredients listed in the Portabella Pappadeaux section in a bowl and mix well. Add additional wine and half & half to slightly thin your cheese mixture as needed. But know, you will want this mixture somewhat dense. Not runny by any means.
Pack filling generously inside of mushrooms tightly. Sprinkle tops with pepper and salt to taste. Top with additional Parmesan and Motzerella Cheese. Top that with additional bread crumbs. Spray tops with butter spray on top to help crisp up the bread crumbs while baking.
Make your easy Hollandaise Sauce with the milk and butter it calls for until thickened up.
Bake mushrooms for 30-35 minutes or, until tops are golden brown. Check periodically for any burning on your cheese tops.
Plate immediately and lightly drizzle with your Hollandaise Sauce. Sprinkle with Paprika if you'd like!
