Preheat oven to 350 degrees
Clean mushrooms and carefully remove stems (keep stems)
Place mushrooms in an oven safe baking dish, cap side down
Put mushrooms in the oven for 5 minutes to soften just slightly
Chop the mushrooms stems
Melt the butter in a saucepan over medium heat
Place the chopped mushroom stems in the saucepan and cook for 3-5 minutes until soft
Add breadcrumbs to the saucepan and cook another 2 minutes
Turn off heat and add the two cheeses and mix well
Taste and add salt as needed
Place the mixture into the mushroom caps until evenly distributed (heaping is good!)
Place back in the oven and cook for 10 minutes or until golden brown on the top
Serve immediately and enjoy!