Pour the oysters with their juices into a medium saucepan. Bring to a simmer, turning the oysters once or twice. As soon as the juices begin to simmer, remove from the heat.
Drain the oysters, reserving the liquor, and set aside.
Return the oyster liquor to a clean saucepan with the chopped shallot and the pastis. Bring to a boil, reduce the heat to a simmer and cook until the volume of the liquid has reduced by half.
Add the cream and bring to the boil. Reduce the heat and simmer for five minutes until the sauce is slightly thickened.
Add the spinach to a pan of boiling water and cook for 1-2 minutes. Drain the spinach and allow to cool slightly. Squeeze all the liquid from the spinach, then coarsely chop the leaves.
Season the spinach with freshly grated nutmeg and freshly ground black pepper, then stir in the parsley with two tablespoons of the cream sauce.
Place three oyster shells onto a baking tray, liberally sprinkled with salt (this will keep the oyster shells from tipping over). Place a teaspoonful of the spinach mixture onto each oyster shell and top with a cooked oyster.
Whisk the egg yolk into the warm cream sauce until thoroughly combined and the sauce is thick and glossy.
Spoon the cream sauce generously over the oysters in their shells, filling the shell as much as possible, then set aside.
For the oysters Kilpatrick, fry the chopped bacon over a medium-low heat until the fat begins to melt and the bacon is golden-brown.
Add the brioche crumbs into frying pan and mix with the bacon until thoroughly combined. Transfer half the crumbs to a small mixing bowl.
Add the Tabasco and Worcestershire sauce to the remaining crumbs in the frying pan. Mix until the crumbs come together.
Place the remaining three oyster shells onto the baking tray. Place teaspoonfuls of the Tabasco crumb mixture onto each empty oyster shell and top with a cooked oyster.
Sprinkle the oysters Kilpatrick liberally with the reserved bacon and brioche crumbs. Dot each oyster with ½ teaspoon of butter.
Place the baking tray with all six oysters under a hot grill for 1-2 minutes until golden brown and bubbling.
Place the oysters on a serving dish that has been liberally sprinkled with salt and serve immediately.