BUTTER-POACHED TRIPLETAIL WITH BRAISED LEEKS, BLACKENED BUTTERNUT SQUASH, AND SAUCE NANTUA

Butter-Poached Tripletail with Braised Leeks, Blackened Butternut Squash, and Sauce Nantua image

Number Of Ingredients 19

Ingredients

1 1/4 cups water, divided
2 lemons, juiced and divided
1 bunch leeks (white parts only) washed, halved lengthwise, and julienned
1 plus 2T cup unsalted butter, divided
1 small butternut squash (1 - 11/4lbs) peeled, seeded, and cut into 1/2" planks
1 tablespoon blackening seasoning
4 skinned tripletail filets (4-5oz) (may substitute grouper or red snapper)
1 tablespoon snipped fresh chives
1 sliced green onion, celery leaves, shaved fennel for garnish
1 Sauce Nantua
1/2 pound shrimp heads or shells
2 celery stalks, roughly chopped
1 small carrot, peeled and roughly chopped
1/2 onion, roughly chopped
1 1/2 teaspoon tomato paste
1 cup white wine
2 cloves garlic, smashed
2 cups heavy whipping cream
1/2 lemon, juiced

Steps:

In a large saute pan, heat 1/4C water and juice of 1 lemon over medium heat. Add leeks in an even layer; cook until softened. Add 2T butter; cook until butter is melted and enough water evaporates to form an emulsion. Season to taste with salt.
In a large bowl, prepare an ice bath. In a large pot, add 2-3 quarts water. Bring to a boil over medium-high heat. Add squash and blanch for 3 minutes in boiling water. Transfer squash to the ice bath to stop cooking; drain when cool and pat dry.
Season squash with salt to taste and blackening seasoning. Heat a cast-iron skillet over high heat. Add squash; sear until caramelized, about 3-4 minutes. Let cool. Cut into bite-sized cubes.
Season fillets with salt. In a wide saute pan, bring remaining 1C water and remaining juice of 1 lemon to a boil over medium-high heat. Reduce heat to a simmer, and place fillets in pan. Steam, uncovered, until fish is about halfway cooked, and liquid is reduced to about 1/2C, about 4 - 6 minutes. Swirl in remaining 1C butter, 2T at a time, adding more liquid if needed to maintain emulsion. Baste fish with butter repeatedly until fish is fully cooked, about 4 minutes. Add chives, and season butter with salt. Spoon Sauce Nantua into a wide bowl. Reheat leeks and squash. Spoon vegetables into center of bowl. Place fish over vegetables, and baste with a little lemon chive butter from pan. Garnish with green onion, celery leaves, and shaved fennel, if desired.
SAUCE: In a medium saucepan, heat a thin layer of oil over high heat. Add shrimp heads; saute until evenly pink. Add celery, carrot, and onion; cook until softened, about 2 minutes. Add tomato paste, and stir to evenly distribute. Stir in wine, and cook for 2 to 3 minutes, scraping browned bits from bottom of pan with a wooden spoon. Add garlic; cook until wine is reduced by half. Add cream, and bring to a boil; reduce heat, and simmer for 20 minutes. Remove from heat. Let cool slightly. Puree mixture using an immersion blender or in batches in the container of a blender. Strain through fine-mesh sieve. Season to taste and add lemon juice.