Rinse oyster shells under cold running water to remove grit. Using a shucking knife and towel, hold the oyster flat-side up, insert the knife at the hinge, twist to pop the shell open, run the blade under the oyster to free it from the bottom shell but keep the oyster in the deeper (bottom) shell. Discard the top shell. Reserve any liquor (juice) in the shell. Place each shucked oyster on a tray of ice to keep cold while you prepare the topping.

Preheat oven to 450°F (230°C). If you have an oven-safe tray with depressions for oysters, use it; otherwise make a bed of coarse salt or crushed ice on a baking sheet to keep shells level.

Rockefeller Topping

Sweat aromatics and greens

In a medium skillet over medium heat, melt 4 tbs unsalted butter. Add the minced shallots and cook 2–3 minutes until translucent (do not brown). Add the minced garlic and cook 30 seconds until fragrant. Add the chopped spinach, parsley, chives and watercress (if using) and cook 2–3 minutes until wilted and reduced.

Deglaze and combine

Pour in 2 tbs dry white wine to deglaze the pan and let it reduce for about 1 minute. Stir in 2 tbs heavy cream and simmer 30–45 seconds to marry flavors. Season with 1/2 tsp salt, 1/4 tsp freshly ground black pepper and the optional 1 tsp Tabasco or a pinch of cayenne. Remove pan from heat and let cool for 2–3 minutes.

Finish topping

Transfer the cooled greens mixture to a bowl. Stir in 1/2 cup finely grated Parmesan and 1/2 cup panko breadcrumbs until evenly combined. Taste and adjust seasoning if needed. If mixture seems too loose, add another tablespoon of panko; if too dry, add a splash (1–2 tsp) of cream or reserved oyster liquor to loosen.

Assemble and bake

Arrange the shucked oysters on the prepared baking tray (on ice bed or in oyster plate) so they are level and stable. Spoon about 1 to 1 1/2 tablespoons of the Rockefeller topping onto each oyster, pressing lightly so it covers the oyster and rests against the shell edges.

Mix 1 tbs melted butter with remaining 2 tbs panko (if you want extra crunch) and sprinkle a small pinch (about 1/2 tsp) of the mixture over each topped oyster. Finish with a light dusting of additional grated Parmesan (optional).

Bake in the preheated 450°F (230°C) oven for 8–10 minutes, or until topping is bubbling and lightly golden. For a crispier browned top, place under the broiler for 1–2 minutes watching carefully to avoid burning.

Remove oysters from oven and let rest 1–2 minutes. Serve immediately on crushed ice or rock salt with lemon wedges alongside.