Huîtres à la Florentine

Ingredients

Equipment Needed

• •Oyster knife and folded kitchen towel or cut-resistant glove
• •Fine-mesh strainer
• •12-inch (30 cm) wide sauté pan
• •1-quart (1 L) heavy saucepan and whisk
• •8-inch (20 cm) skillet for poaching
• •13 by 18-inch (33 by 46 cm) rimmed sheet pan
• •Heavy-duty aluminum foil

Instructions

1. 1

   Open the oysters

   Set an oven rack 5 to 6 inches (13 to 15 cm) below the broiler and heat it fully. Scrub the closed oysters under cold running water. Protecting your hand with a folded towel or cut-resistant glove, shuck each oyster over a bowl so every drop of liquor is caught. Free the oyster from both muscles, keep it chilled in its liquor, and reserve the twelve deep shell halves. Discard any oyster with a broken shell, an offensive smell, or a shell that remained gaping when tapped before opening. Strain the liquor through a fine sieve to remove grit, then rinse and dry the empty deep shells.

2. 2

   Stew spinach dry

   Melt the spinach butter in a wide sauté pan over medium-high heat. Add the shredded spinach in batches, turning each addition until it collapses, then season with half the salt. Continue cooking, stirring and spreading the spinach across the hot surface, until the pan holds no visible liquid and a spoon drawn through it leaves a dry trail. This is the step that decides the dish. If liquid gathers after the spinach rests, return it to the hot pan and cook it away before assembling. Ça se rattrape. Transfer the spinach to a plate so it stops cooking.

3. 3

   Build the Mornay

   Melt the Mornay butter in a small heavy saucepan over medium-low heat. Stir in the flour and cook this roux blanc, a white roux, for 1 to 2 minutes without letting it brown. Add the 3/4 cup (180 ml / 185 g) warm milk gradually, whisking each addition smooth, then whisk in the cream. Bring the sauce to the gentlest simmer and cook for 3 to 4 minutes, stirring, until it thickly coats the back of a spoon. Remove it from the heat before adding the Gruyère, Parmesan, white pepper, nutmeg, and remaining salt. If it becomes grainy or oily, the cheese met too much heat. Take the pan off the stove and whisk in cold milk, 1 teaspoon at a time, until the Mornay comes together again. Taste before adding any more salt, because the oysters and cheeses already carry plenty.

4. 4

   Poach the oysters

   Pour the strained oyster liquor into a small skillet, adding only enough water to make a shallow poaching bath if the oysters yielded very little. Bring it to a bare tremble, never a rolling boil. Slip in the oysters and poach for 20 to 30 seconds, turning once, just until their thin edges begin to curl while the centres remain plump. Lift them out promptly with a slotted spoon. They will finish beneath the broiler, so a full poach here would turn them firm before they ever reach the table.

5. 5

   Fill the shells

   Crumple strips of foil across a rimmed sheet pan to make twelve stable nests, then settle a deep shell into each one. Divide the spinach among the shells, using about 1 tablespoon in each and keeping it in a compact bed. Lay one poached oyster over every portion. Spoon enough warm Mornay over each oyster to mask it completely, about 1 generous tablespoon, without flooding the shell.

   Test the tray with a gentle nudge before it goes near the broiler. A rocking shell spills its sauce, and hot Mornay is a miserable thing to retrieve from the oven floor.
6. 6

   Glaze and serve

   Broil the oysters for 2 to 4 minutes, watching without wandering away, until the Mornay bubbles around the edges and takes mottled golden colour. Rotate the tray if your broiler heats unevenly. If the tops brown before the sauce bubbles, lower the tray by one rack and continue briefly; fierce heat should glaze the sauce, not scorch it while the oyster stays cool. Serve immediately on a stable platter, warning guests that the shells are hot. À table!

Chef Tips

• •Choose oysters with deep lower shells and a clean smell of cold seawater. Flat, brittle shells are awkward to fill, while a deep cup keeps the spinach, oyster, and Mornay where they belong.
• •Keep live oysters cupped-side down under a damp towel in the refrigerator at 34 to 40°F (1 to 4°C). Never submerge them in fresh water or close them in an airtight container, and shuck them as near to cooking as possible.
• •The broiler must be fully heated before the tray goes in. A weak glaze leaves the oysters waiting under heat while the sauce slowly colours, which is how plump oysters become tight little buttons.
• •For guests who are pregnant, older, immunocompromised, or otherwise vulnerable to raw shellfish, cook the oyster centres to 145°F (63°C) for at least 15 seconds. The texture will be firmer, but safety comes first.
• •Pour a mineral Chablis, Muscadet, or brut Champagne. The wine needs enough acidity to meet the oyster and enough backbone for the butter, cream, and cheese.

Advance Preparation

• •The Mornay can be made up to one day ahead. Press parchment directly against its surface, chill it promptly, then reheat over gentle heat and loosen it with a little milk if it has tightened.
• •The spinach can be stewed up to four hours ahead, cooled promptly, and refrigerated. Check it again before assembly; if it has released moisture, return it to a hot pan until dry.
• •Scrub the oyster shells and prepare the foil nests earlier in the day, but leave the oysters closed and cold until shortly before poaching. Once assembled, the shells should go beneath the broiler within 15 minutes.

Frequently Asked Questions

Nutrition Information

1 serving (about 180g)