Luxurious vegetarian centerpiece: crisp golden puff pastry encasing a savory duxelles of wild field and chestnut mushrooms with shallots, garlic, thyme, and wilted spinach.
Sauté mushrooms, shallots, and garlic in butter over medium-high heat for 12 minutes until all moisture evaporates and mixture is rich and concentrated. Cool completely.
Ensure wilted spinach is squeezed bone-dry in a kitchen towel. Season with salt, pepper, and nutmeg.
Unroll puff pastry. Layer spinach down the center, top with mushroom duxelles, and shape into a neat log. Wrap pastry over, crimp seams, and chill 20 minutes.
Score decorative pastry slits, brush with beaten egg, and bake at 200°C for 28-32 minutes until puffed, crisp, and deep golden brown.