1. Make the guacamole: mash the avocados, lime juice, salt, cayenne, onion and garlic in a bowl until well combined. (Note: many guacamole recipes call for cilantro and tomatoes, these are left out because of the cucumber topping).
2. Make cucumber topping: mix cucumber, black sesame, and soy sauce in a small bowl.
3. Make tapas: coat each cracker in a spoonful of guacamole, than heap a small spoon of cucumber mixture on top.
5. Serve soon! These will stay good for about 30 minutes but then start to get soggy.