In a double-boiler top; combine oil, flour, mustard,vinegar, sugar ,salt. pepper and paprika.
Cook and stir, over boiling water until thickened.
In a small bowl, slightly beat egg yolk; stir in sour cream. Beat in a small amount of the hot vinegar mixture. Then sit egg yolk mixture into rest of hot liquid; cook stirring, over hot water 3 to 4 minutes, or until slightly thickened. Cool 10 minutes. Now beat egg whites with a rotary beater just until soft peaks form.Still using the beater, beat egg white into cooled dressing until well combined. Refrigerate until ready to use; then add cooled dressing and toss until well combined. Chill for 2 hours.