Potato-Crusted Lyonnaise Fish
FOR THE BEURRE BLANC:
3/4 cup white wine
2 tbsp. lemon juice
6 whole black peppercorns
3 cloves garlic, finely chopped
14 tbsp. unsalted butter, cubed and chilled
FOR THE GARNISH:
4 tbsp. butter
1 large onion, halved and thinly sliced lengthwise
1/4 cup capers
FOR THE FISH:
2 russet potatoes, peeled
1/4 cup canola oil, plus more for frying
1/2 cup flour
1/2 cup milk
1 egg, beaten
4 5-oz. boneless red snapper filets
Kosher salt and freshly ground black pepper, to taste
1. Make the beurre blanc: In a 10" skillet over medium-high heat, combine the wine, lemon juice, peppercorns, and garlic and cook until reduced to 2 tbsp., about 6 minutes. Set a fine strainer over a 1-qt. nonreactive saucepan set over low heat; strain wine mixture. Working with 14 tbsp. butter, whisk in 2 tbsp. at a time, waiting until the butter is emulsified before adding more, until sauce is slightly thick and smooth. Season sauce with salt and set aside in a double boiler over low heat to keep warm.
2. Make the garnish: Heat 2 tbsp. butter in a 10" nonstick skillet over medium-high heat. Add the onions and cook, stirring occasionally, until caramelized, about 12 minutes. Transfer onions to a plate; set aside. Add remaining butter to the skillet over high heat. Add capers and cook, stirring frequently, until crisp, 4 minutes. With a slotted spoon, transfer capers to the plate with the onions; set aside.
3. Make the fish: Julienne potatoes lengthwise using the narrowest setting of a French mandoline. (For similar results, use the large wholes on a box grater.) Transfer potatoes to a strainer and rinse under cold water, turning and squeezing potatoes, until the water runs clear. Let drain for 5 minutes and pat dry with paper towels.
4. Pour oil into a 4-qt. saucepan to a depth of 2". Heat over medium-high heat until a thermometer reads 250°. Working in batches, cook the potatoes until just tender, about 3 minutes. Using a slotted spoon, transfer potatoes to paper towels. Divide into 8 portions and set aside.
5. Place the flour in a shallow dish. Whisk together the milk and egg in another shallow dish. Season the filets with salt and pepper and toss to coat in the flour; shake off excess flour. Dredge filets in the egg wash. Place each filet on top of a portion of potatoes and cover with another portion of potatoes, pressing lightly to adhere.
6. Heat oven to 200°. Heat 2 tbsp. oil in a 12" nonstick skillet over medium-high heat. Using a metal spatula, transfer 2 filets to the skillet. Cook, flipping once, until the potatoes are crisp and golden and fish is cooked through, about 12 minutes; transfer to a wire rack set over a baking sheet and keep warm in the oven. Wipe out the skillet and repeat with the remaining oil and filets.
7. To serve, spoon some of the beurre blanc onto a warm plate. Add a potato-crusted filet and sprinkle with toasted capers and caramelized onions.