Sear 3 portobello mushrooms in a pan with a tablespoon of oil for approx 5 minutes then set aside. In the same pan, add 1 chopped leek and 1 diced onion along with minced garlic and a pinch of chopped thyme. Once the onion and leeks are softened, add the spinach, pecans and chestnuts. Stir until the spinach has wilted.
Next, take 1 tablespoon of Maille Wholegrain mustard and stir through the mixture and take the pan off the heat.
Flour a clean, dry surface and lay out one sheet of ready rolled vegan puff pastry. Brush your pastry with 1 tbsp of Maille Dijon Mustard and completely coat the topside. Place your nut mixture, horizontally along the top half of your pastry sheet. Top the nut mixture with the 3 portobello mushrooms. Take the remaining pastry and fold over the mushrooms. Seal the edges with a fork and glaze the top with soy milk.
Bake in the oven at 180℃ for 25 minutes.
Slice into portions and serve with your favourite roasted vegetables.