In a large pot, melt 4 tablespoons of butter over medium to medium-high heat until it foams. Gradually stir in 4 tablespoons of flour, whisking constantly for about 5 minutes until a blonde roux develops, smooth and slightly golden in color.

Add 1 cup of chopped onion, 1 cup of diced bell pepper, and 1 cup of diced celery to the roux. Sauté for 2 minutes until softened and fragrant.

Pour in 2 cups of milk and 1 cup of reserved oyster liquor, stirring well. Add 1-2 tablespoons of Cajun seasonings, plus salt and pepper to taste. Cook for 3-4 minutes, allowing the mixture to thicken slightly.

Incorporate 2 cups of fresh shucked oysters, ¼ cup of chopped parsley, ¼ cup of sliced green onions, 2 minced garlic cloves, and 1-2 teaspoons of hot sauce. Bring to a gentle boil and cook for 3-4 minutes until oysters are tender.

Remove from heat, adjust seasoning as needed. Ladle into bowls and garnish with parsley and green onions. Serve hot with soda crackers or oyster crackers.