Remove puff pastry from refrigerator 20–30 minutes before using so it becomes pliable but still cold. Preheat oven to 220°C (425°F). Line a baking sheet with parchment paper. Lightly flour a work surface with the 2 tbs flour and unfold one sheet of pastry. Using a sharp knife or pizza cutter, score a 1 cm border around the perimeter of each pastry sheet without cutting through (this creates a raised edge). Prick the center area lightly with a fork to prevent excessive rising.

Egg wash

In a small bowl beat together the egg and 1 tsp water until combined. Brush the outer 1 cm border of each pastry sheet with egg wash to promote browning and seal later if stacking layers.

Bake pastry shells

Bake the scored pastry sheets on the prepared sheet for 10–12 minutes, until the edge is puffed and golden and the centers are mostly set. Remove from oven and let cool slightly. If centers puff too much, gently press them down with a spatula while still warm to flatten.

Final assembly and finishing

When mushroom sauce and braised leeks are ready, spoon an even layer of braised leeks onto each pastry center (reserve a small amount of cooking liquid). Top with a generous layer of shiitake mushroom sauce. Sprinkle with the 2 tbs snipped chives, and season edges with remaining sea salt and pepper to taste. Serve warm or at room temperature cut into 6–8 starter portions.

Braised leeks

Trim, halve lengthwise, and thinly slice the white and light green parts of the leeks. Rinse thoroughly to remove grit and pat dry.

Heat 2 tbs butter and 1 tbs olive oil in a medium skillet over medium-low heat until butter foams. Add the sliced leeks and a pinch of the 0.5 tsp fine sea salt. Sauté gently, stirring occasionally, for 6–8 minutes until softened but not browned.

Add 60 ml stock, increase heat to medium, cover, and let the leeks braise for 5–7 minutes until tender and most liquid has evaporated. Uncover and stir; finish with 1 tsp lemon juice (optional) to brighten flavor. Taste and adjust salt if needed. Keep warm until assembly.

Shiitake mushroom sauce

Clean mushrooms by wiping with a damp cloth; slice shiitakes and other mushrooms uniformly. Pat dry to avoid excess water in the pan.

In a large sauté pan over medium-high heat melt 2 tbs butter. Add the sliced mushrooms in a single layer (work in batches if necessary) and cook, undisturbed for 2–3 minutes so they brown, then stir and continue until golden and any released liquid has mostly evaporated, about 6–8 minutes total.

Reduce heat to medium, push mushrooms to the side and add the minced shallot and garlic to the pan. Cook 1–2 minutes until fragrant and translucent, stirring so they don’t burn.

Deglaze the pan with 60 ml white wine or vermouth, scraping up brown bits from the bottom. Let the wine reduce by half, about 1–2 minutes.

Add 120 ml stock, 1 tsp soy sauce, and 1 tsp fresh thyme leaves. Simmer gently for 3–4 minutes to concentrate flavor.

Stir in 60 ml heavy cream and simmer for 1–2 minutes to warm through. If the sauce needs thickening, mix 1 tsp cornstarch with 1 tbs cold water to make a slurry and whisk into the simmering sauce; cook 1 minute until slightly thickened. Season with 0.5 tsp salt and 0.25 tsp black pepper, tasting and adjusting as needed.

If you prefer a smoother, slightly glossy sauce, transfer half of the mixture to a blender or use an immersion blender to purée briefly, then fold back into the pan to retain some mushroom texture. Keep warm until assembly.