Brown bacon; add garlic when nearly brown. Add butter and shallots. After cooking a few minutes, add spinach and all other ingredients. Thicken with enough breadcrumbs to make thick, and simmer for about 10 minutes. Have 12 pie pans half filled with rock salt. Arrange 6 oyster shells in each pie pan. Top each oyster at room temperature in its shell until heated through and browned on top.
While you can't get real absinthe here in the United States, it is illegal, you can get many other liquors that taste very similar, and they are labeled as absinthe.