This unusual soup, a Bergeron invention, was perhaps inspired by the soup called boula boula, a purée of pea soup and turtle soup that was popularized by Jacqueline Kennedy in the early 1960s. Trader Vic's uses jarred Pacific coast oysters for this dish.
1 10-oz. package partially thawed frozen spinach
6 shucked oysters and their liquor
2 tbsp. bottled clam juice
1 small clove garlic, peeled and chopped
Freshly ground white pepper
4 cups half-and-half
1 tbsp. butter
2 tbsp. A.1. Steak Sauce
1⁄2 tsp. Tabasco
1⁄2 tsp. worcestershire sauce
1⁄2 tsp. cornstarch
3 tbsp. heavy cream, chilled
1. Put spinach, oysters and their liquor, clam juice, garlic, and pepper to taste into a medium nonreactive pot over medium-high heat. Bring to a simmer, breaking up spinach with the back of a spoon, and simmer until heated through, about 5 minutes. Transfer to a blender and purée until very smooth. Set spinach–oyster mixture aside.
2. Preheat broiler. Bring half-and-half to a simmer in a medium pot over medium heat. Whisk in butter, then spinach–oyster purée, and return to a simmer. Add steak sauce, Tabasco, worcestershire, and salt to taste. Dissolve cornstarch in 1 tbsp. water, then whisk into soup. Keep soup warm over lowest heat.
3. Whisk cream in a bowl until soft peaks form. Divide soup between 4 shallow heatproof soup bowls and put a big spoonful of the whipped cream on top of each. Place bowls of soup under broiler briefly to brown cream, then serve soup immediately.