Remove stems from mushrooms, and scoop out dark brown "gills" with a teaspoon while keeping the mushroom cap intact. Preheat oven to 400 degrees.
Melt butter in a large skillet over medium heat. Add pepper and garlic, and saute for 2 to 3 minutes. Add venison and Italian seasoning, and saute until just cooked. Cool mixture.
In a medium bowl, combine cooled venison mixture with breadcrumbs, pepper flakes and cheese. Mix well, and season to taste with salt and pepper.
Divide mixture evenly into 4 parts. Each portion should stuff 4 mushrooms caps (with some left over). Spoon mixture into caps, and place on a lightly greased baking pan. Place in the preheated oven for 6 to 7 minutes or until cheese is melted.