Let cool slightly, cut lengthwise in half. Scoop out most of the inside of the potatoes, leaving about 1/4 inch thick potato walls to form a "bowl". Set the potato "bowls" aside.
Mash the potato that you scooped out
saute the onions and green onions in the butter in a frying pan. Cook about 10 - 15 minutes or until the onion is done. At this point add the mushrooms and cook 3 minutes before adding the crabmeat and shrimp. Add some ground black pepper to taste.
Add the vermouth, bring to a boil, stirring constantly until all the liquid is gone.
Stir in the dairy products, using half of the cheese. Pour this into the mashed potato bowl. Stir well. If you think you need more ground black pepper and half and half, add it now. Stir well again.
Put this filling into the reserved potato "bowls", place them on baking sheet. Sprinkle with remaining cheese. Bake at 375 degrees until the cheese is melted and bubbly.