In bowl, combine gelatin and boiling water; stir until completely dissolved. Stir in salt, mustard and Worcestershire; chill until consistency of unbeaten egg whites. Add cucumber, onion, parsley, vinegar and sour cream. Lightly oil or rinse 4 cup (1 L) mould, with cold water. Pour in gelatin mixture. Chill 2 hours or until set.

Unmoulding tips:

Carefully loosen salad from sides of mould with moistened tip of sharp knife. Dip mould into warm (not hot) water to the depth of salad for about 5 seconds. Remove from water and tilt or shake mould gently to loosen salad. Invert serving dish on top of mould. Hold both firmly together and turn over. Shake firmly until salad slips down from mould onto serving dish. If salad doesn't come loose easily, repeat process.