Add milk, onion, and egg and stir just until blended.
Pour about 2 inches of oil into a Dutch oven, large pot or deep pan. Heat oil to 375 degrees.
Drop dough by rounded teaspoonfuls into oil and fry until golden on all sides. Fry in batches and do not overcrowd the pan or the oil temperature will drop too much. Remove with a slotted spoon to a paper towel-lined plate. Serve warm.