Preheat oven to 375 degrees.
Wash your mushrooms and allow them to dry. I usually use paper towel to do this because it is faster than letting them sit, upside down, on a tea towel.
Open cans of shrimp and crab and drain well. Set aside.
Prepare a rimmed baking sheet with tinfoil and place your mushrooms on top and paint each with olive oil.
Bake for 4-5 minutes in the oven to soften sothey don’t drip water when you bite into them.
Remove mushrooms from oven and when cool enough to handle remove each stem. Reserve stems for another use.
In a large mixing bowl combine cream cheese, sour cream, grated or shredded cheese, garlic, shrimp, crab, green onions and pepper. Blend really well.
Pour and scrape contents of the bowl into a resealable bag. Press mixture into one of the bottom corners and then cut the corner off.
Squeeze mixture in to mushroom caps one at a time. Press bag deep inside of each mushroom to get as much in there as possible making sure there is extra on top of the mushroom. Not overflowing but my husband always says it's like making a soft serve ice cream! In some ways he is right I suppose!
Place filled mushroom caps on top of rack back on your prepared baking sheet. Bake for about 15 minutes or until cheese is melted and nice and brown. Serve immediately and enjoy!