Sole Florentine

Ingredients

Equipment Needed

• •Shallow 3-quart broiler-safe gratin dish
• •12-inch sauté pan with lid or parchment
• •4-quart wide pot for the spinach
• •2-quart heavy saucepan and balloon whisk
• •Broad fish spatula

Instructions

1. 1

   Dry the spinach

   Put the washed spinach in a wide pot with only the water clinging to its leaves. Cover and cook over medium-high heat for 2 minutes, then turn the leaves and continue just until they collapse. Drain, let them cool enough to handle, and squeeze them firmly by the handful until no stream of water falls. Shred the spinach across the leaves. Wipe the pot dry, melt 3 tablespoons of the butter, and stew the spinach uncovered for 5 to 7 minutes with ¼ teaspoon of the salt and a pinch of white pepper. It should be dark green and glossy but leave no wet trail in the pot. If liquid gathers, don't assemble the dish. Tip the spinach into a sieve, press it again, and return it to the buttered pot for another minute. Ça se rattrape.

   The squeezing is not rough treatment. Spinach carries astonishing amounts of water, and any left behind will run into the gratin and thin the Mornay.
2. 2

   Build the Mornay

   Reserve ¼ cup of the milk, then warm the remaining milk and the cream in a 2-quart saucepan until the edge barely trembles. Pour the hot dairy into a jug. Melt 4 tablespoons of butter in the same saucepan, whisk in the flour, and cook for 2 minutes over medium-low heat, keeping the roux pale and gently frothing. Add the hot dairy a quarter at a time, whisking each addition smooth before the next, then simmer gently for 5 to 7 minutes until the sauce coats the back of a spoon in an even ivory layer. Remove it from the heat and stir in ½ cup of the Gruyère and ¼ cup of the Parmesan. Season carefully with salt and white pepper. If the Mornay tightens too far, whisk in the reserved milk a spoonful at a time; if the cheese turns oily, take the pan off the heat and whisk in a spoonful of that milk until the sauce comes together again.

   Add the cheese away from direct heat. Boiling after the cheese goes in can make a smooth Mornay grainy, and the broiler will give it all the heat it needs later.
3. 3

   Poach the sole

   Melt 2 tablespoons of butter in a 12-inch sauté pan, add the fish fumet, and bring it only to a bare tremble. Season the sole lightly on both sides, folding each thin tail underneath so the fillets cook evenly, then arrange them in one layer. Cover with a lid or a round of parchment and poach gently for 3 to 5 minutes, depending on thickness, until the flesh is pearly and just opaque at its thickest point. The fumet must never boil; if it starts, lift the pan off the heat at once and let the residual warmth finish the fish. Transfer the fillets with a broad spatula to a rack or clean towel and let their surfaces drain for a minute.

4. 4

   Assemble the gratin

   Set an oven rack 5 to 6 inches beneath the broiler and heat the broiler to high. Use 1 tablespoon of butter to coat a shallow 3-quart broiler-safe gratin dish. Spread the hot spinach in an even layer, arrange the drained sole over it without crowding, and check the Mornay. It should be hot and fluid enough to fall in a thick ribbon; loosen it with a little reserved milk if necessary. Napper, meaning coat completely, the sole with the Mornay, then scatter the remaining ¼ cup Gruyère and ¼ cup Parmesan evenly over the surface.

5. 5

   Glaze it quickly

   Set the gratin dish on a rimmed sheet pan and place it beneath the broiler for 2 to 4 minutes. Watch without leaving the stove. The sauce should bubble at the edges while the cheese turns butter-gold with bronze patches; rotate the dish if one side colors first, and shield any spot that darkens too quickly with a small piece of foil. This is glazing, not baking, so take the dish out as soon as the crown is ready. Let it settle for 2 minutes, then carry it straight to the table. À table!

Chef Tips

• •Dover sole is splendid here, but good skinless lemon sole or similarly thin flounder fillets will take the method honestly. Match the fillets by thickness so the poaching finishes at the same moment.
• •A clean, lightly seasoned fish fumet matters more than a strong one. Taste before salting anything else; concentrated or heavily salted stock can overwhelm sole and turn the finished Mornay harsh.
• •The broiler replaces the salamander, but it must be fully heated and close to the dish. A weak, prolonged glaze cooks the sole twice and loosens the sauce; fierce heat and a watchful eye give color before either can happen.
• •Strain the used fumet, boil it for a minute, cool it promptly, and keep it refrigerated for up to 2 days. It has taken on the sole's flavor and makes a fine foundation for another fish sauce.
• •Pour a restrained white Burgundy, Chablis if you have it, whose acidity can stand against the Mornay without bullying the sole. Cooking well is not cooking fancy.

Advance Preparation

• •The spinach can be wilted, squeezed, shredded, and stewed in butter up to 1 day ahead. Chill it promptly, then reheat it until thoroughly hot and dry before assembling the gratin.
• •The Mornay can be prepared up to 1 day ahead. Press buttered parchment directly against its surface, refrigerate, and reheat gently while whisking in a little milk if it has tightened.
• •Poach the sole and assemble the dish close to serving. Do not ask the broiler to reheat a cold gratin; its work is the quick glaze, and leaving the dish beneath it longer will toughen the fish.

Frequently Asked Questions

Nutrition Information

1 serving (about 500g)