In a large bowl, lightly beat egg with a fork. Add cream, crumbs, salt and pepper. Stir and let stand until crumbs are moistened. Add beef, potatoes and onion. Mix well with a wooden spoon or your hands (mixture will be soft). Cover and refrigerate for 1 1/2 hours or until well chilled.
With moistened hands, form mixture into 3/4 -inch balls. Place on lightly greased 15 1/2 x 10 1/2 x 1-inch jelly roll pans. Bake immediately or cover and refrigerate up to 24 hours.
Bake in a preheated 400° oven for 18 to 20 minutes or until browned and cooked through. Drain meatballs on paper towels if necessary.
Serve on a warming tray or thread meatballs onto wooden picks with pickled onions, pineapple chunks, marinated mushrooms or cherry tomatoes.