Sauté onion in bacon drippings and butter in a small skillet until tender. (Do not brown.) Dissolve bouillon cubes and sugar in boiling water. Combine sautéed onion, bouillon mixture, and beets in container of an electric blender; process 2 minutes or until smooth.
Transfer mixture to a heavy saucepan, and heat thoroughly. (Do not boil.) Ladle into individual soup bowls, and serve warm. Garnish each serving with a dollop of sour cream. Borscht may also be served chilled.