In a skillet over medium heat, melt butter. Saute mushrooms, onion & garlic until onions & garlic are soft & most of the moisture has been released from the mushrooms, about 3-5 minutes. Set aside to cool.
Preheat oven to 400 F. Line a baking tray with parchment paper.
In a large bowl, combine cooled veg mixture, pork, breadcrumbs & seasonings; mix all ingredients until incorporated. Shape mixture into 1 1/2-inch meatballs.
Cut thawed puff pastry into thin strips. Wrap each meatball with a few strips of the pastry & place on the baking sheet. Brush pastry with egg wash.
Bake 25-30 minutes or until golden & meat is cooked through. Remove from oven & place on serving platter. These are nice to serve with steamed broccoli, mashed potatoes and mushroom gravy.