Oyster Stew for One or Two

INGREDIENTS

• 2 tablespoons butter
• 1 (6 inch) celery rib, finely chopped
• 1 small clove garlic, minced
• 1 tablespoon all-purpose flour
• 1 cup milk
• 1/4 cup half-and-half cream
• 1/4 teaspoon onion powder
• 1 pinch dried parsley
• 1/2 teaspoon salt
• 1 cup fresh shucked oysters, undrained
• 1 pinch ground black pepper, to taste