1. Melt butter and add flour. Remove from heat and gradually stir in milk and sour cream.
2. Stir until well combined and sauce thickens.
3. Simmer for 5 minutes over low heat. Cool slightly.
4. Blend sauce and avocado in a blender until smooth.
5. Chop prawns finely, reserving 12 for garnish. Mix through avocado sauce.
6. Add mustard and freshly ground pepper.
7. Sprinkle gelatin over water and dissolve over hot water.
8. Add gelatin to avocado mixture. Cool to lukewarm.
9. Mix through mayonnaise and lemon juice.
10. Spoon into 6 individual dishes or bowls and refrigerate for a few hours.
11. Garnish with chopped parsley, 2 prawns each person and a little finely sliced California Avocado.
12. Serve with Melba toast or croutons.

*Large avocados are recommended for this recipe. A large avocado averages about 8 ounces. If using smaller or larger size avocados adjust the quantity accordingly.