Drain oysters, reserving 1/4 cup liquid; set oysters and liquid aside.
Cook bacon in a large nonstick skillet over medium heat until crisp; drain, reserving 1 teaspoon drippings in pan. Crumble bacon; set aside.
Add shallots and mushrooms to pan; cook, stirring constantly, over medium-high heat 3 minutes. Add reserved oyster liquid; cook 1 minute, stirring well. Reduce heat to medium.
Combine flour and 1/4 cup milk, stirring with a whisk until smooth; stir in remaining milk. Add milk mixture to mushroom mixture; bring to a simmer over medium heat. Cook 3 minutes or until mixture thickens, stirring frequently. Stir in sherry, oysters, shrimp, salt, and pepper; bring mixture to a simmer. Cook 2 minutes or until shrimp turn pink.
Cut toasted bread in half diagonally; place 2 toast points on each of 4 individual serving plates. Spoon mixture evenly over toast points. Sprinkle with crumbled bacon and chives.