Directions

• Process 3 oysters, 2 cups cold water, and 1/2 teaspoon salt in a blender until completely smooth, about 45 seconds. Pour mixture through a fine wire-mesh strainer into a medium bowl; discard any solids. Season to taste with up to 1 teaspoon additional salt if needed to reach a salty-tasting solution. Set aside. Reserve remaining oysters in an airtight container in refrigerator while you prepare bisque.
• Heat a large Dutch oven or heavy-bottomed soup pot over medium 3 minutes; add butter. Once butter is melted, add onions and 1/2 teaspoon salt; cook, stirring occasionally, until onions are soft and translucent, 10 to 12 minutes.
• Add sliced white and light green parts of scallions, celery, and garlic to pot; cook, stirring often, until fragrant, about 2 minutes. Stir in reserved oyster liquid, heavy cream, hot sauce, black pepper, cayenne, and remaining 1/2 teaspoon salt. Bring to a simmer over medium-high. Reduce heat to medium-low, and simmer, uncovered, stirring occasionally, until celery is tender, about 10 minutes. Stir in potatoes; simmer, stirring occasionally, until fork-tender, 10 to 15 minutes. Stir in reserved oysters; simmer, stirring occasionally, until plump, about 5 minutes. Stir in parsley stems; adjust seasonings to taste.
• Ladle bisque evenly into bowls; garnish with reserved sliced scallion tops, chopped parsley leaves, and hot sauce. Serve with saltines or crusty bread.