Roasted Halibut with Vegetables en Papillote

Preheat the oven to 375°. In a saucepan of boiling water, cook the carrots for 1 minute. Add the asparagus and sugar snaps and cook until crisp-tender, 2 minutes. Drain and spread on a plate to cool.

In a nonstick skillet, heat the 2 tablespoons of oil until shimmering. Add the onion and mushrooms, season with salt and pepper, and cook over moderately high heat, stirring until softened, 7 minutes. Transfer to the plate; let cool slightly.

Heat 2 large, sturdy baking sheets in the oven. Lay out eight 14-inch-long sheets of parchment paper and brush with olive oil. Mound some of the vegetables on half of each sheet. Set the fillets on the vegetables and season with salt and pepper. Fold each packet in half, then fold up 2 sides to seal, leaving 1 side open. In a small bowl, combine the stock and sherry; spoon 1 1/2 tablespoons into each packet. Fold up the last side, sealing tightly.

Transfer the packets to the preheated baking sheets. Bake for 9 minutes, until the fish is cooked through. Open the packets and transfer the fish, vegetables and broth to plates. Serve at once.