Poached Fish Fillets with Sherry-Tomato Vinaigrette

Fillets of meaty white fish like cod, halibut, sea bass, or snapper work best in this recipe. Just make sure the fillets are at least 1 inch thick. A neutral oil such as canola can be substituted for the pure olive oil. The onion half in step 3 is used to displace the oil; a 4-ounce porcelain ramekin may be used instead. Serve with couscous or steamed white rice.

Ingredients

Fish

• 4(6-ounce) skinless white fish fillets, 1 inch thick
•   Kosher salt
• 4ounces frozen artichoke hearts, thawed, patted dry, and sliced in half lengthwise
• 1tablespoon cornstarch
• 3/4cup olive oil
• 3 garlic cloves, minced
• 1/2 onion, peeled

Vinaigrette

• 4ounces cherry tomatoes
• 1/2small shallot, peeled
• 4teaspoons sherry vinegar
•   Kosher salt
• 1/2teaspoon pepper
• 1tablespoon chopped fresh parsley
• 2ounces cherry tomatoes, cut into 1/8-inch-thick rounds

Instructions

• 1. FOR THE FISH: Adjust oven racks to middle and lower-middle positions and heat oven to 250 degrees. Pat fish dry with paper towels and season each fillet with 1/4 teaspoon salt. Let sit at room temperature for 20 minutes.
• 2. Meanwhile, toss artichokes and cornstarch in bowl to coat. Heat 1/2 cup oil in 10-inch nonstick skillet over medium heat until shimmering. Shake excess cornstarch from artichokes and add to skillet; cook, stirring occasionally, until crisp and golden, 2 to 4 minutes. Add garlic and continue to cook until garlic is golden, 30 to 60 seconds. Strain oil through fine-mesh strainer into bowl. Transfer artichokes and garlic to ovenproof paper towel–lined plate and season with salt. Do not wash strainer.
• 3. Return strained oil to skillet and add remaining ¼ cup oil. Place onion half in center of pan. Let oil cool until it registers about 180 degrees, 5 to 8 minutes. Arrange fish fillets, skinned side up, around onion (oil should come roughly halfway up fillets). Spoon a little oil over each fillet, cover skillet, transfer to middle rack, and cook for 15 minutes.
• 4. Remove skillet from oven. Using 2 spatulas, carefully flip fillets. Cover skillet, return to middle rack, and place plate with artichokes and garlic on lower-middle rack. Continue to cook fish until it registers 130 to 135 degrees, 9 to 14 minutes longer. Gently transfer fish to serving platter, reserving 1/2 cup oil, and tent fish loosely with aluminum foil. Turn off oven, leaving plate of artichokes in oven.
• 5. FOR THE VINAIGRETTE: Process whole cherry tomatoes, shallot, vinegar, 3/4 teaspoon salt, and pepper with reserved 1/2 cup fish cooking oil in blender until smooth, 1 to 2 minutes. Add any accumulated fish juice from platter, season with salt to taste, and blend for 10 seconds. Strain sauce through fine-mesh strainer, pressing on solids to extract as much liquid as possible (discard solids).
• 6. To serve, pour vinaigrette around fish. Garnish each fillet with warmed crisped artichokes and garlic, parsley, and tomato rounds. Serve immediately.

Technique

• Poaching Fish Out of Water

  Oil poaching is not only a foolproof technique for cooking delicate fish but also a seamless way to create a crispy garnish and elegant sauce from the same oil.
  
• FRY GARNISH
  When the recipe calls for it, frying artichoke hearts or scallion whites in oil yields a crisp garnish that provides a nice contrast to the fish.
• COOL HOT OIL 
  Pouring 1/4 cup of fresh oil into the strained frying oil helps cool it to a gentle poaching temperature.
  
• DISPLACE OIL 
  Adding an onion half displaces the oil, so it comes up higher in the pan—and we can use less of it.
• TRANSFER TO OVEN 
  Poaching in a low oven (rather than on the stove) guarantees more even cooking.
  
• MAKE VINAIGRETTE 
  Using the flavorful poaching oil to create a simple vinaigrette adds brightness.
  

Technique

Why Poach in Oil?

Poaching in oil allows fish to retain more of its juices than poaching in wine or broth, leading to remarkably moist, velvety results. This is because cooking in oil is inherently more gentle than cooking in water. And while you might expect that fish poached in fat would be greasy, it actually absorbs very little oil. Why? In order for oil to penetrate the fish, moisture must exit first. But because oil and water repel each other, it’s very difficult for moisture inside the fish to readily enter the oil. Hence, more of the juices stay in the fish. In fact, in our tests, oil-poached fish lost just 14 percent of its weight during cooking, while water-poached fillets lost 24 percent.