First, clean mushrooms and remove mushroom stems. Discard the stems.
Preheat the oven to 400℉. The, pre-bake the mushrooms upside down for 15 minutes. This will release a bunch of water but let them cool before handling later.
Before cooking raw shrimp press them between paper towels to release some of the excess water so that they can sear in the pan and not boil.
On a high heat frying pan add oil then add shrimp. Season with salt and pepper and cook shrimp until pink and right before they're done add in the minced garlic. Allow them to cool, this won't take long.
Chop up the cooled shrimp into small pieces before making the filling.
Add shrimp to a bowl then add cream cheese, mayo, lemon juice now tasteful salt and pepper. Note, the mix should be creamy, not loose and runny. If runny you'll need more cream cheese.
Microwave 1TB of butter and mix breadcrumbs, parmesan cheese and that melted butter together. You can skip the parmesan cheese and just add another tablespoon of breadcrumbs. Note, only the breadcrumbs give a crispy crunch.
Spoon shrimp into each mushroom. Now take breadcrumb topping and sprinkle over each mushroom. Place in preheated oven for 20 minutes or until tops are golden brown.Remove then allow to cool before serving.