Grill corn over a gas flame, grill, or under the broiler. Once browned, remove corn from cob with a knife. As an alternative, remove corn from husk and sauté in olive oil in a small pan over medium heat until browned.
Zest lemon and set aside.
Place corn, lemon juice, avocado flesh, cucumbers, sorrel leaves and garlic in a food processor and process until combined. Add water, olive oil and salt and pepper to taste and process. Strain through a fine mesh strainer and chill for at least one hour.
Once chilled, put into serving bowls (two main course, four appetizer) and garnish with avocado chunks, sorrel leaves, lemon zest and red chili pepper flakes.