Start by preparing the mushroom paste (also called duxelles). Place the mushrooms, shallots, garlic, thyme, salt and pepper in the bowl of a food processor. Process until the mushrooms are very finely chopped.

Heat the tablespoon of oil in a large skillet over medium heat. Once hot, add the mushroom mixture and cook for 10-15 minutes, or until mushrooms have released their moisture and there is no liquid left. Stir regularly to prevent burning. Once the mixture appears almost dry, remove from heat, transfer to a bowl or plate and set aside.

Preheat oven to 375°F (190°C).

To prepare the seitan roast: heat the olive oil in a large skillet over medium heat. Once hot, add the diced onion, garlic, and grated ginger. Cook for about 3 minutes or until onions become translucent.

Next, add the sliced mushrooms and cook for another 5-7 minutes. Once the mushrooms are cooked, deglaze the pan with the soy sauce and maple syrup. Cook for 1 minute and then transfer to a food processor.

To the food processor, add the cooked brown rice, red kidney beans, beet, almond flour, oregano, and spices. Process for 7-10 seconds, or until the mixture forms a slightly chunky paste.

Transfer the paste to a large mixing bowl. Add the vital wheat gluten and mix until fully incorporated. Don't overmix as it would make the roast too chewy. Shape it into a large log.

To assemble the vegan Wellington: lay out the sheet of puff pastry on a layer of plastic wrap. Spread the mushroom mixture in the center of the puff pastry, leaving about 2 inches on each side. Place the seitan log on top of the mushroom paste. Brush the log with a generous amount of yellow mustard. Using the plastic wrap, carefully roll the puff pastry tightly around the seitan roast. Seal both ends by pinching the puff pastry.

Place the Wellington on a baking sheet lined with parchment paper and remove the plastic wrap.

In a small bowl, combine the almond milk and maple syrup to make a vegan 'egg' wash. Brush the top and sides of the Wellington with the egg wash and sprinkle with coarse sea salt.

Bake for 45-50 minutes, or until the pastry is golden brown. Remove from the oven and let it cool 5-10 minutes before cutting into thick slices.

Serve with your favorite gravy or peppercorn sauce and roasted potatoes and/or greens on the side!