Strain the oyster juice through a fine-meshed sieve into a bowl to remove any grit. Reserve the juices.

Rinse the oysters well, under cold water. Put them in a bowl.

Melt the butter in a pot over medium heat. Add the flour and stir to make a roux. Reduce the heat to medium-low and cook the mixture for a few minutes, stirring often. When the roux turns the color of coffee-with-cream, stir in the celery and onions. Increase the heat to medium and cook for 2-3 minutes, stirring frequently.

Add the oyster juice and any juices the oysters in the bowl have released. The flour in the roux will absorb the liquid and turn into a paste. Slowly add the milk and cream, stirring to incorporate as you pour them in. Add a healthy splash or two of hot sauce, to taste. Heat the soup to steamy, but below a simmer, over low heat, cook for 15 minutes. (Do not let the soup boil!) If you are working with large oysters, you may want to chop them into bite-sized pieces. Add the oysters and cook for another 2 minutes, or until the edges of the oysters just begin to curl.

Add salt and freshly ground black pepper to taste. Garnish with fresh chopped parsley or sliced green onions.

Serve hot with crackers.