Poached Arctic Char with Brown Butter and Shiitake

Nutty brown butter and tart fresh lemon complement arctic char’s rich flavor, and the accompanying shiitake and sugar snap peas add texture and earthy sweetness. If you can’t find arctic char, use wild-caught Pacific salmon instead.

• 4 5- to 6-oz. skinless arctic char fillets (about 3/4 inch thick)
• Kosher salt
• 6 oz. (3/4 cup) plus 2 Tbs. unsalted butter
• 8 thin lemon slices plus 1 Tbs. juice (from 1 medium lemon)
• 4 quart-size Ziploc storage or freezer bags
• 8 oz. shiitake mushrooms, stemmed and quartered (4 cups)
• 4 oz. sugar snap peas, strings removed and thinly sliced on the diagonal (1-3/4 cup)
• 1/2 tsp. toasted sesame seeds
• 1/8 tsp. crushed red pepper flakes

Pat the fish dry and season on both sides with 1 tsp. salt total. Transfer to a plate, cover with plastic wrap, and chill for 1 to 2 hours.

Have ready a small, fine strainer set over a small heatproof bowl. In a 1- to 2-quart saucepan, melt the 3/4 cup butter with 4 of the lemon slices over medium heat, swirling frequently, until the milk solids turn golden-brown, 6 to 8 minutes. Immediately strain the butter, pressing on and then discarding the lemon slices. Let cool to room temperature.

Divide the butter and the remaining 4 lemon slices among the 4 bags. Put 1 piece of fish in each bag. Seal the bags, pressing out as much air as possible, and gently massage the fish to coat it all over.

Fill a 4-quart pot with 3 inches of water and clip a deep-fat, probe, or instant-read thermometer to the side of the pot. Heat the water slowly over low heat to 140°F, about 15 minutes. Put the bags of fish in the water (the tops of the bags can stick out) and cook, maintaining a water temperature of 135°F to 145°F, until the center of the fish registers 130°F to 135°F on an instant-read thermometer (open the bags to check), 10 to 12 minutes. Transfer the bags to a rimmed baking sheet and let sit for 5 minutes.

Meanwhile, melt the remaining 2 Tbs. butter in a 12-inch skillet over medium heat until foamy, then add the mushrooms and a pinch of salt. Cook, stirring often, until the mushrooms are light golden, 3 to 5 minutes. Add the peas and 2 Tbs. of water and cook, stirring often, until the peas are bright green and crisp-tender, about 2 minutes. Add 1/4 tsp. of the sesame seeds and the red pepper flakes, then season to taste with salt.

Using scissors, snip off one corner of each bag and drain the butter into a small bowl. Stir the lemon juice into the butter and set aside. Divide the mushrooms and sugar snap peas among 4 dinner plates. Open each bag and cut down the center perpendicular to the seal. Using a spatula, lift the fillets from the bags and arrange on top of the vegetables. Pour the reserved lemon-butter mixture over the fish, garnish with the lemon slices and the remaining 1/4 tsp. sesame seeds, and serve.