Shuck each oyster, reserving the juice. Separate the oyster from the muscle, leaving the oyster in the bottom of the shell and discarding the top shell. Place the half shells on a baking sheet filled with rock salt to keep the oysters from tipping. Strain the oyster juice through cheesecloth or a fine sieve, and set aside.
Bring some water and butter to a boil in a large pot. Add the spinach and salt & pepper and simmer until spinach is wilted. Drain the spinach thoroughly , getting as much liquid out as possible. Chop spinach finely and set aside.
In a heavy pan, sauté the bacon until crisp. Pour off most of the grease and add the onion and garlic. Sauté 3 minutes. Add the Pernod and bring to a flame. Add the butter, Worcestershire, Tabasco and reserved oyster juice. Bring to a simmer and add the spinach, bread crumbs and cheese mixture. The mixture should be moist, but not too wet.
Top each oyster on the half shell with a spoonful of the topping and bake at 350 degrees for 8-10 minutes