Preheat oven to 350F (175C). Grease a 15x10x1 inch baking pan. Remove and discard the stems from the mushrooms, and reserve the caps. Arrange mushroom caps on the baking sheet
. Cook beef, green onion, celery, onion, garlic and salt in a large skillet until the vegetables are tender and meat is browned. Drain off the fat. Stir in milk, parsely and breadcrumbs. Spoon mixture into the mushroom caps. Bake
10 to 15 minutes or until mushrooms are tender and heated through.