1. Put the oysters in a strainer over a medium bowl to catch their liquor. Reserve 175ml of the oyster liquor. In a large bowl, combine the crumbled cornbread and oysters.
2. Bring a small saucepan of water to a boil. Add the bacon and cook for one minute. Drain and pat dry with kitchen towel.
3. Melt 115g of the butter in a large skillet over medium-high heat. When the foaming subsides, add the bacon, shallot, celery, salt, and season with pepper, to taste. Cook, stirring, until soft, about ten minutes. Add the parsley, thyme, reserved oyster liquor, and vermouth and bring to a boil. Transfer the shallot-herb mixture to the cornbread and oysters and stir to combine. Set aside for ten minutes. Preheat the oven to 200°C/ gas mark 6.
4. Transfer the cornbread mixture to a buttered 1-litre gratin dish, dot with the remaining butter, and bake until browned and crusty, about one hour.
5. Remove from the oven and serve immediately.
Cook's Note: Try to find already shucked oysters in their liquor (juice) in small plastic tubs at your local supermarket or seafood monger.
6. Preheat the oven to 200°C/ gas mark 6. In a large bowl, whisk together the polenta, flour, baking powder, sugar, and salt.
7. In a medium bowl, whisk the egg and combine with the milk. Pour the milk mixture into the polenta mixture and mix lightly with a rubber spatula until a thick batter is formed. Stir in the melted butter until just incorporated.
8. Spoon the batter into the prepared pan. Bake until lightly browned and a toothpick inserted in the center comes out clean, about 30 minutes. Let cool.