Rinse oysters under cold running water to remove grit. Using an oyster knife and thick glove or towel, carefully shuck each oyster, retaining as much of the liquor (natural juices) in the shell as possible. Discard the top shells and place the half shells with oysters on a baking sheet lined with a layer of coarse kosher salt to keep them steady.

Preheat your oven to 500°F (260°C) or set broiler to high. Arrange shucked oysters on the prepared baking sheet so they sit level in the salt bed. Keep baking sheet near the oven so oysters don't sit too long before topping.

After baking, serve immediately with lemon wedges. (See topping/broiling steps below before serving.)

Topping Mixture

Prepare spinach

Place the chopped spinach in a dry skillet over medium heat and cook for 1–2 minutes, stirring, just until wilted and bright green. Remove to a fine mesh strainer or paper towel and press to remove excess moisture. Chop more finely if needed and set aside.

Sauté aromatics

In a medium skillet over medium heat, melt 4 tablespoons of the unsalted butter. Add the minced shallots and cook 2–3 minutes until softened and translucent but not browned. Add the minced garlic and cook 30–45 seconds until fragrant.

Build topping

Reduce heat to low. Add the chopped parsley, wilted and drained spinach, chopped scallions, Worcestershire sauce, Pernod (if using), hot sauce (if using), salt and pepper to the skillet. Stir to combine and cook 1–2 minutes to marry flavors. Remove skillet from heat and stir in the remaining 2 tablespoons butter until melted and incorporated.

Finish topping

Transfer mixture to a bowl and fold in the toasted breadcrumbs and grated Parmesan. Taste and adjust seasoning with additional salt, pepper, or a few drops of lemon juice if desired. The topping should be moist but hold together when pressed; add an extra teaspoon of breadcrumbs if too wet.

Top oysters and broil

Using a small spoon, place about 1 heaping tablespoon of the topping mixture over each shucked oyster, covering the oyster and a little of the shell rim. Sprinkle a light dusting of additional Parmesan and a pinch of toasted breadcrumbs on each for a crisp finish. Place the baking sheet with oysters under the preheated broiler (or in 500°F oven) about 4–6 inches from the heat and broil for 3–5 minutes, watching closely, until topping is bubbly and golden brown (edges slightly charred).

Remove oysters from oven. Let cool 1 minute, then transfer oysters to a serving platter or keep them in the salt bed. Serve immediately with lemon wedges.