You can purchase shucked oysters from your local fish market. The oysters should be plump and fresh-smelling. Chef Holiday Recipes Made EasyPlus: More Appetizer Recipes and Tips
Preheat the oven to 350°. Spread the bread with 3 tablespoons of the butter and arrange the slices, buttered side up, on a large baking sheet. Toast for about 10 minutes, or until golden brown and crispy. Cut the toasts in half diagonally.
In a medium saucepan, combine the reserved oyster liquor and the wine and bring to a simmer over moderately high heat. Add the oysters and simmer over low heat until their edges start to curl, about 3 minutes. With a slotted spoon, transfer the oysters to a plate; reserve the oyster-poaching liquid.
In a large skillet, cook the bacon over moderate heat, stirring occasionally, until crisp, about 8 minutes. Using a slotted spoon, transfer the bacon to paper towels to drain. Pour off all but 1 tablespoon of the bacon fat from the skillet and add the remaining 1 tablespoon of butter. Add the leeks, celery and onion and cook over low heat, stirring occasionally, until softened, about 10 minutes. Stir in the flour and cook for 1 minute. Slowly add the reserved oyster-poaching liquid, whisking constantly, until smooth. Simmer over low heat, whisking often, until no floury taste remains, about 3 minutes. Whisk in the milk, cream and thyme and simmer for 3 minutes longer, until thickened and creamy. Stir in the lemon juice, then season with salt, pepper and Tabasco. Fold in the oysters and cook just until warmed through, about 1 minute.
Arrange 2 toast halves on each of 10 plates. Spoon the creamed oysters on top, sprinkle with the bacon and serve at once.
The fruit flavors of a Champagne will point up the saltiness of the oysters and the bacon; the acidity will cut the creamy sauce.