First Step: PREPARE THE FILLING

1. Cook the Vegetables: Heat 2 tablespoons of olive oil in a large pan over medium heat. Add the chopped onion and sauté for 3-4 minutes until softened. Add the garlic and cook for another 1-2 minutes until fragrant.
2. Add the Mushrooms: Add the chopped mushrooms to the pan and cook for 7-8 minutes until they release their moisture and start to brown. Stir occasionally to ensure the mushrooms cook evenly.
3. Add the Spinach: Stir in the chopped spinach and cook for an additional 2-3 minutes until wilted. If there’s excess moisture in the pan, cook for a little longer to let it evaporate.
4. Season the Filling: Stir in the soy sauce, black pepper, nutmeg, thyme, and rosemary. Taste and adjust seasoning as needed.
5. Add the Lentils and Bind the Filling: Add the cooked lentils to the pan and mix everything together. Stir in the breadcrumbs and Dijon mustard to help bind the filling together. Let the mixture cool slightly while you prepare the puff pastry.

Second Step: ASSEMBLE THE WELLINGTON

1. Roll Out the Puff Pastry: On a lightly floured surface, roll out the two sheets of puff pastry into a rectangle large enough to wrap the filling completely. The size should be about 12 inches by 15 inches, depending on how thick you want the Wellington.
2. Place the Filling: Once the filling is slightly cooled, spoon it into the center of the rolled-out puff pastry. Shape the filling into a log or rectangle shape, leaving a border around the edges of the pastry.
3. Wrap the Wellington: Carefully fold the sides of the pastry over the filling, tucking in the ends as you go. Make sure the filling is completely enclosed. If the pastry edges don’t seal well, use a little water to pinch them together.
4. Brush with Egg Wash: Transfer the wrapped Wellington to a baking sheet lined with parchment paper. Brush the entire surface of the pastry with a beaten egg to create a golden, glossy finish when baked.
5. Make Slits for Steam: Using a sharp knife, make a few shallow slits across the top of the Wellington to allow steam to escape during baking.

Third Step: BAKE THE WELLINGTON

1. Preheat the Oven: Preheat your oven to 400°F (200°C). This temperature ensures that the pastry bakes to a crisp, golden perfection while the filling remains warm and moist.
2. Bake the Wellington: Place the Wellington in the preheated oven and bake for 30-35 minutes, or until the pastry is golden brown and puffed up. You may need to rotate the Wellington halfway through baking to ensure even cooking.
3. Rest the Wellington: Once the Wellington is done, remove it from the oven and let it rest for 5-10 minutes before slicing. This resting period helps the filling set and makes it easier to slice without spilling out.

Fourth Step: GARNISH AND SERVE

1. Slice the Wellington: Carefully slice the Vegetarian Wellington into 6-8 portions, making sure to cut through the flaky pastry without crushing the filling.
2. Garnish and Serve: Garnish with fresh herbs like parsley or thyme for an extra touch of color and flavor. Serve the Wellington with a side of vegetarian gravy or a fresh salad.