Make Spice Sachet with 2 tsp coriander, 2 tsp fennel seeds, 1 tsp peppercorns, ½ tsp chili flakes and 1 tsp mustard seeds.
For Citrus Marinade: Combine 2 cups Florida orange juice, ⅓ cup lime juice, ⅓ cup lemon juice, 1½ cups rice wine vinegar, 2½ Tbsp. sugar, 2 tsp curry powder, ½ tsp turmeric and Spice Sachet in pot large enough to hold shrimp.
Bring to boil. Reserve 2 cups to make Citrus Vinaigrette. Add shrimp, garlic, jalapeño, cilantro and red onion. Bring back to simmer and cook for an additional 2-3 minutes and then remove pot from heat.
Pour into plastic nonreactive or glass container and refrigerate overnight.
To make Citrus Vinaigrette: Combine 1 Tbsp cornstarch and 1 Tbsp cold water. Bring 2 cups reserved citrus marinade to boil and whisk in cornstarch mixture. Bring to simmer until thickened. Cool and reserve.
To serve, fan avocado slices on plates. Place shrimp on top and drizzle with Citrus Vinaigrette.
Garnish with cilantro leaves.