Grounded Meatballs

INGREDIENTS FOR MEATBALLS • 1lb ground beef, I use ground sirloin • 1/4 cup breadcrumbs • 1/4 cup milk • 1 egg • 1 yellow onion, finely chopped • 2 cloves garlic minced • salt and pepper to taste • INGREDIENTS FOR MUSHROOM GRAVY • 2 cups mushroom slices • 2tbs olive oil • 2 cups be