Mushroom Wellington

Ingredients

• 2 tbsp olive oil
• 3 tbsp unsalted butter
• 2 shallot – finely chopped
• 3 cloves garlic – minced
• 24 ounces brown mushrooms (cremini/chestnut) – finely chopped
• 8 ounces wild mushrooms – finely chopped
• 2 tsp thyme – finely chopped
• 1.25 tsp kosher salt
• 0.75 tsp ground black pepper
• 0.33 cup dry sherry
• 0.5 cup all-purpose flour
• 0.75 cup whole milk
• 1 large egg
• 1 tbsp unsalted butter – melted
• 6 ounces baby spinach
• 2 tbsp Dijon mustard
• 14 ounces puff pastry sheet, thawed
• all-purpose flour – for dusting
• 1 large egg – beaten (egg wash)
• flaky sea salt – for serving

Instructions

1. Make the mushroom duxelles: Finely chop the mushrooms (or pulse in a processor). Heat the olive oil and 3 tbsp unsalted butter in a large skillet over medium-high heat. Add the shallots and cook until softened, 3–4 minutes; stir in the garlic for 30 seconds. Add the brown and wild mushrooms, thyme, kosher salt, and black pepper. Cook, stirring often, until they release liquid and then turn dry and sizzle, 12–18 minutes. Pour in the dry sherry, scrape up any browned bits, and cook until almost dry, 3–5 minutes. Spread the mixture on a tray to cool completely, about 15 minutes.
2. Make two thin crêpes: Whisk the all-purpose flour (0.5 cup), whole milk, and the large egg until smooth; reserve a little melted butter for the pan, then whisk the rest into the batter. Rest 5 minutes. Heat a nonstick skillet (8–10 inches) over medium heat and lightly brush with the reserved butter. Pour in just enough batter to film the pan, swirl, and cook until set and lightly golden, 30–45 seconds per side. Make 2 crêpes and let them cool.
3. Wilt the spinach: In the same skillet over medium heat, add the baby spinach and cook, tossing, until just wilted, 1–2 minutes. Transfer to a clean towel and squeeze out excess moisture, then roughly chop.
4. Build the filling log: On a sheet of parchment, overlap the two cooled crêpes to make a wrapper wide enough to enclose the filling. Brush with the Dijon mustard. Arrange the cooled duxelles in a compact 8-inch-long log across the center and scatter the chopped spinach over it. Use the parchment to help roll the crêpes tightly around the filling, tucking in the ends. Wrap in the parchment and chill until firm, 15–20 minutes.
5. Wrap in pastry: Heat the oven to 400°F (200°C) with a rack in the lower third. On a lightly floured surface (use the all-purpose flour for dusting), roll the puff pastry sheet to roughly 12×14 inches. Transfer the pastry to a parchment-lined baking sheet. Unwrap the crêpe log and place it seam-side down along the lower third of the pastry. Roll the pastry up and over to enclose; brush the final edge with a little water and press to seal. Trim any excess and tuck the ends under so the seam is down.
6. Finish the top: Lightly score the pastry with a sharp knife in a crosshatch pattern, taking care not to cut through. Brush all over with the beaten large egg. Chill the wrapped Wellington 15–20 minutes to firm the pastry.
7. Bake until deep golden brown and crisp, 35–45 minutes; the pastry should be puffed and the bottom should feel set and sound hollow when tapped. Rest 10 minutes to set the layers.
8. Slice thickly and sprinkle with flaky sea salt (for serving). Serve immediately while the pastry is crisp.