Ingredients

• 4 ounce sole fillets
• 2 leeks, white and light green parts sliced into 1/4-inch rings, rinsed
• 8 ounce mushrooms, sliced thin
• 4 tablespoon unsalted butter
• 0.5 cup dry white wine
• 2 tablespoon fresh lemon juice
• 2 teaspoon fresh thyme, leaves only
• 1 teaspoon fresh tarragon, minced
• 0.5 teaspoon kosher salt
• 0.25 teaspoon white pepper
• 1 tablespoon fresh parsley, minced

Steps

1. Preheat the oven to 400°F (205°C).
2. Cut four 12-inch squares of parchment paper and set aside.
3. Heat 2 tablespoons of butter in a large skillet over medium heat. Once foaming, add the sliced leeks and cook for 4 minutes, stirring occasionally, until softened and beginning to turn translucent.
4. Add the sliced mushrooms to the skillet and cook for 3 minutes until they release their moisture and begin to brown slightly.
5. Remove the skillet from heat and season the vegetable mixture with 1/4 teaspoon salt and a pinch of white pepper. Set aside to cool slightly.
6. Pat the sole fillets dry with paper towels. Season both sides of each fillet lightly with remaining salt, white pepper, and fresh thyme.
7. Place each parchment square on a work surface and divide the cooked leek-mushroom mixture into four equal portions, placing each portion in the center-left half of each parchment square.
8. Lay one sole fillet on top of each vegetable portion.
9. Pour 2 tablespoons of white wine and 1/2 tablespoon of lemon juice over each fillet. Top each with 1/2 tablespoon of the remaining butter (4 small pats total) and divide the fresh tarragon among the packets.
10. Fold each parchment square in half to create a triangle, then crimp and fold the edges tightly to seal the packet completely, ensuring no steam can escape.
11. Place the sealed parchment packets on a baking sheet and bake for 12 to 15 minutes until the parchment is puffed and lightly golden brown.
12. Carefully remove the baking sheet from the oven. **WARNING: The parchment packets are extremely hot and filled with steam — use kitchen shears or a sharp knife to make a small slit in each packet for steam to escape before opening, to avoid burns.**
13. Open the packets carefully, tearing back the parchment to reveal the fish. Check the thickest part of each fillet with an instant-read thermometer — it should reach 145°F (63°C).
14. Transfer each unopened packet to a warm serving plate, or carefully slide the contents onto individual plates, ensuring the leeks, mushrooms, and fish stay together.
15. Garnish each plate with fresh minced parsley and serve immediately while the fish and vegetables are still steaming hot.