This is another recipe from my childhood. I can still remember my mom making this for parties and it was one of my favorites.
When I make this for a party it is also one of the favorites for the guests.
I usually double or quadruple the recipe for a larger party.
Clean mushrooms then remove and slice up the stems
Brown the ground beef, add the mushroom stems, onion and ham, cook until onion is nearly done
Add remaining ingredients and simmer until until cooked.
Place mushrooms onto a cookie tray (line tray with parchment paper or silicone map to make cleanup easy)
stuff mixture into the mushroom caps. sprinkle with grated mozza and parmesan
place tray of mushrooms under the broiler for about 5 minutes