Sauté onion and jalapeno over medium heat till tender, about 12-15 minutes. Add garlic and sauté briefly, about two minutes. Remove from heat and set aside.
Place chopped avocados in blender with chicken broth, 4 TBL of the lemon juice, and sauté mix. Puree till smooth.
Transfer to a large bowl; stir in water and lemon zest. Add water if desired to achieve your preferred thickness. Taste and season with salt and pepper. Refrigerate, covered, for 3 hours.
In a separate bowl, mix the crab, cucumber, and the remaining tablespoon of the lemon juice. Salt and pepper to taste. Refrigerate, covered 1-3 hours.
Ladle soup into bowls; top with shrimp mixture. Garnish with 2-3 chive stems.
Cook’s notes: Lovely with corn bread and a simple salad of citrus, walnuts, and Boston lettuce – and if you want to garnish it with a few wedges of avocado, so much the better!