Place crab boil, water and salt in pot with 2 quarts water. Bring to boil for 5 minutes. Add shrimp and boil gently for 5 minutes.
Remove from heat and let stand 20 minutes to cool. Peel, devine and shred boiled shrimp in blender.
Add mayonnaise and grated onion, if desired. Salt and pepper to taste and add a little hot sauce.
Serves 8 to 10.
Cajun Country -- New Iberia, Louisiana