Remove the casings from the sausages. Break the sausage into a skillet over medium heat. Cook while working the sausage into small pieces with a kitchen fork, until the sausage begins to brown. Pour off any excess fat.
Add the crushed red pepper, oregano, and salt. Add 1/2 cup of water, turn the sausage and continue to break up the pieces until all the pink is gone.
Add the parsley and bread crumbs and mix in well. Add a little water or chicken stock if needed to keep the mixture from being very dry. (It should not be very wet, either.) Remove from the heat.
While the sausage is cooking, remove the stems from the mushrooms. Slice off a sliver the size of a dime from the top of the mushroom cap to make a flat area.
While the sausage mixture is still warm, use a teaspoon to stuff the bottom of each mushroom. Pile as much stuffing on as will stay in place, with some perhaps crumbling off. Place the mushrooms stuffing side up on a baking pan. Top with a generous pinch of the shredded cheese (as much as you can get to stay put) on top of the stuffing.
Broil until the cheese melts and begins to brown. Remove and serve very hot.