1. Spoon sour cream into a 1-qt. zip-top plastic bag. Snip 1 corner of bag to make a small hole; pipe sour cream into 6 (2-oz.) shot glasses.
2. Combine avocado and next 3 ingredients in a bowl. Mash with a fork, and season with salt and pepper to taste.
3. Spoon avocado mixture over sour cream in shot glasses. Top each with tomato, egg, and 1/2 to 1 tsp. caviar. Reserve remaining caviar for another use. Serve parfaits with breadsticks and assorted crackers.
Party Tip: We used less expensive, shelf-stable lumpfish caviar found near the canned tuna. It costs around $5 for a small jar. Another affordable choice is salmon caviar. Its bright orange color would look stunning atop each parfait. Try fresh caviar if your seafood department stocks it. It may cost a tad more, but you only need a few teaspoons.