1 tablespoon (15 milliliters) extra virgin olive oil or butter
1 leek (white part only), sliced
525 grams) cremini mushrooms, sliced
2 teaspoon (10 milliliters)
chopped fresh thyme
Salt and black pepper
30 milliliters brandy
1/2 cup (65 grams) dry breadcrumbs
120 grams Brie cheese, cut into pieces
2 sheets (450 grams) butter puff pastry,
340 grams fresh asparagus, trimmed and blanched
1 egg mixed with 2 tablespoons (30 milliliters) of milk, for egg wash
Heat a large sauté pan over medium-high heat and add the oil (or butter), leek and mushrooms. Sauté the mushrooms until they are fully cooked and any liquid has evaporated, about ten minutes. Stir in the thyme and season lightly with salt and pepper, cooking the mixture for a minute more. Add the brandy and remove the mushrooms from the heat to cool to room temperature. Stir in the breadcrumbs and the pieces of Brie.
Preheat the oven to 400°F (200°C) and line a baking tray with parchment paper.
Place the puff pastry sheets on top of each other on a work surface. Use a sharp knife to trim off two strips, each 36 millimeters wide, from opposite sides (creating a rectangle shape) of each piece of pastry and set aside. (You will have four strips in total.)
Place one sheet of pastry onto the prepared baking tray. Brush the edges with the egg wash and use the reserved strips to create a frame on the pastry base, trimming them as needed so that they fit snugly and then brushing them with the egg wash. Spread the mushroom mixture within this frame, pressing it in firmly. Arrange the asparagus spears in a row onto of the mushrooms pressing in gently.
Place the second sheet of pastry overtop, stretching it if needed, to have it reach the edges of the base pastry. Brush the top of the Wellington with the egg wash. Using kitchen scissors, snip little air vents into the top of the Wellington.
Bake for ten minutes and then reduce the oven to 375°F (190°C) and cook for another 35 to 40 minutes, until the pastry is a rich golden brown. Allow the Wellington to cool for ten minutes before slicing to serve.