Preheat the oven to 250 degrees F.
Trim the crust off the bread. Slice the bread into 1/2-inch cubes. Spread the bread on a baking sheet and toast for 20 to 30 minutes, or until dry, being careful not to develop any color. Set aside.
Raise the oven temperature to 350 degrees F.
Melt 1 tablespoon of the butter.
Brush a 2-quart casserole or gratin dish with the melted butter and set aside.
In a large saute pan, add 1 tablespoon of the butter and melt. Add the spinach and cook over high heat until wilted. Drain the spinach and set aside.
To the same saute pan, over medium heat, add the remaining 7 ounces butter. Add the onion and the garlic and saute until translucent, about 2 to 3 minutes. Add the mushrooms and continue to saute another 5 minutes. Add the oysters, oyster juice, sausage, spinach, dried fruits, and salt and pepper. Cook for 3 minutes and stir until the mixture is well blended. Set aside.
In a large bowl, lightly beat the eggs. Add the cream and milk. Stir until well blended. Add the parsley, sage, rosemary, and thyme. Add the reserved oyster mixture and the toasted bread and mix well. Taste and adjust seasoning with salt and pepper. Transfer to the buttered casserole dish and bake for 45 minutes or until done.