Ingredients

2 to 3 cups rock or coarse salt, for baking sheet 

2 dozen oysters, shucked, liquor and bottom shells reserved separately 

1 cup heavy cream 

1 cup dry champagne or sparkling wine 

3 large shallots, minced (about 1/2 cup) 

1/4 cup white-wine vinegar 

2 1/2 sticks (1 1/4 cups) cold unsalted butter, cut into pieces 

Coarse salt and freshly ground white pepper 

1 pound fresh or frozen spinach, thawed 

Snipped fresh chives, for garnish 

Preparation

Pour salt into a rimmed baking sheet. Nestle oyster shells in the salt; set aside.

Bring cream to a boil in a saucepan. Reduce to simmer; cook until reduced by half. Remove from heat; set aside.

Meanwhile, place champagne, shallots, and vinegar in another small saucepan. Bring to a simmer, and cook until the liquid is almost evaporated. Add the reduced cream, and cook for 1 minute.

Remove pan from heat, and whisk in the butter, 1 piece at a time, adding each new piece before the previous one has melted completely. (The sauce should not get hot enough to liquefy. It should be the consistency of thin hollandaise.) Add 1/2 cup oyster liquor to the sauce, and season with salt and white pepper. Keep warm.

If using fresh spinach, rinse it thoroughly several times, and place in a saucepan with just the water that clings to the leaves. Cover the pan, and cook spinach until bright green and just tender, about 2 minutes. Drain well, and roughly chop. (Squeeze excess moisture from thawed frozen spinach).

Preheat broiler with rack 5 inches from the heat source. Divide spinach equally among the shells. Top with a shucked oyster. Spoon on enough sauce to cover the oyster, about 1 tablespoon per shell. Place under the broiler until sauce bubbles and edges of oysters start to curl, about 1 minute. Garnish with chives, and serve.