Slice liver into 2 inch cubes. Sauté the onions in oil until transparent. Drain and remove onions to bowl. Fry liver in same pan, stirring frequently, until fully cooked (about 10 minutes). Remove liver to bowl with onions; mix thoroughly and refrigerate overnight. In a meat grinder or food processor, add liver and onions and 3 eggs; grind until smooth paste. Add mayonnaise and salt to taste; mix well. Serve with mini rye breads or crackers. Garnish with radishes or tomato wedges.