One 1½-pound turbot--filleted, skin removed and bones reserved
8 ounces cremini mushrooms, thinly sliced
6 cups water
¼ cup dried morel mushrooms
2 tablespoons butter
1 yellow onion, thinly sliced
Kosher salt, to taste
½ cup heavy cream
Thinly sliced red pearl onions, for garnish
Lemon thyme leaves, for garnish
Directions
Make the pickled chanterelles: Place the chanterelles in a heatproof bowl. In a small saucepan, bring the remaining pickle ingredients to a boil over high heat. Pour over the mushrooms and let cool completely.
Meanwhile, prepare the turbot: Preheat the oven to 400º and line a baking sheet with parchment. Place the turbot bones on the prepared baking sheet and roast until golden brown, 10 minutes.
Transfer the bones to a medium saucepan with the cremini mushrooms, water and dried morels. Bring to a simmer over medium heat and cook until reduced to 4 cups, 45 minutes. Strain the broth, discarding solids and return the liquid to the pan. Bring to a simmer and cook until reduced by half, another 20 to 25 minutes.
While the broth is simmering, melt the butter in a 12-inch skillet over medium heat. Add the onion and cook, stirring often, until well caramelized, 20 to 25 minutes. Season with salt, then transfer to a cutting board and finely chop; set aside.
Transfer the reduced mushroom broth to a 12-inch skillet. Heat over medium heat until it reads 180º on an instant-read thermometer. Season with salt, then add the turbot fillets to the broth. Poach the fillets until opaque and cooked through, 1 to 2 minutes.
Using a fish spatula, transfer the fillets to shallow bowls. To the broth, stir in the heavy cream and season with salt. Ladle some of the broth over each fillet, then scatter a few pickled chanterelles around the fish.
Garnish with a quenelle of the chopped caramelized onions, a few rings of red pearl onions and lemon thyme leaves, then serve.