Preheat oven to 180 degrees C /gas mark 4.
Pour the cream into a bowl and soak the breadcrumbs in it.
Heat butter and oil in a large frying pan over medium heat. Add onion and cook, stirring often, until tender. Transfer to large bowl and wipe pan clean.
Add beef, egg, nutmeg, allspice, garlic and cooked onion to breadcrumb mixture. Use your hands to blend well and shape into 4cm meatballs.
Place in a glass pryex dish. Cover with foil and cook in oven for 20-30 minutes or until cooked through.