- 1 pound asparagus, trimmed and cut into 1-inch pieces
- 1 cup vegetable stock
- ¼ cup blanched spinach (optional)
- 3 sprigs fresh dill
- 2 tablespoons white miso paste
- 2 tablespoons extra-virgin olive oil
- 1 large leek, washed and sliced in ½-inch-thick rounds (white and light green parts only)
- 3 clusters (2–3 cups) oyster mushrooms, tough bottoms removed
- 4 (5-ounce) fluke (or other fresh fish) filets, skin removed
- Kosher salt
- 1–2 teaspoons yellow mustard seeds, coarsely ground
- 3 tablespoons unsalted butter, divided
- 1 clove garlic, thinly sliced
- 1 shallot, minced
- 1 small head of romaine lettuce, washed and cut into 1-inch ribbons
- 1 tablespoon fresh lemon juice
Preheat oven to 300°F.
Bring a large pot of water to a boil and blanch asparagus for 3 minutes, or until very tender. Immediately transfer to ice water bath to stop the cooking and let chill completely for several minutes. Place drained asparagus, vegetable stock, optional spinach, dill, miso paste and olive oil in a blender and purée for 2 minutes, until very smooth. (Fine-strain through a sieve for finer consistency, if desired.) Transfer to a sauce pot and set aside. (This can be done in advance and refrigerated.)
Soak sliced leek rounds in cold water to remove any dirt. Gently lift leeks out of the water and place on paper towels to dry. Separate mushrooms into strands and set aside.
Pat dry the fluke filets and season tops with kosher salt and cracked mustard seeds. Heat a large nonstick sauté pan over medium-high heat and add 1 tablespoon butter. When butter is browned, add fluke, seasoned side down, and sear until golden brown, 2 to 3 minutes. Transfer to a sheet pan lined with parchment paper, seasoned side up, and place in oven for 10 to 13 minutes. While the fish is in the oven, slowly warm the asparagus purée as you finish the vegetables.
Return sauté pan to medium heat, add 2 tablespoons butter, sliced garlic and minced shallots and sauté for about 1 minute. Add leek rounds and brown on both sides, then add mushrooms and sauté for 3 to 5 minutes more. Add lettuce at the last minute and season with a few drops of lemon juice.
To serve, divide the mushroom, leek and lettuce mixture in the center of 4 warm, large, shallow bowls. Place fluke atop the vegetables and pour the asparagus purée around the fish. Serve immediately.