|Unflavored gelatin||1 Ounce (1 Envelope)|
|Cold water||1 Cup (16 tbs)|
|Minced yellow onion||1 Tablespoon|
|Cayenne pepper||1 Pinch|
|Pureed avocado||1 Cup (16 tbs) (About 2 Small Ripe Ones)|
|Mayonnaise/Sour cream||1⁄4 Cup (4 tbs)|
Sprinkle gelatin over water, then heat and stir until dissolved.
Mix in remaining ingredients, spoon into an ungreased 3-cup mold, cover tightly, and chill until firm.
Unmold (especially pretty on a bed of watercress) and serve at once (the mousse discolors rapidly on standing); wrap any leftovers airtight.