Creating Lentil Wellington is a straightforward process if you follow these simple steps:

1. Cook Lentils: Rinse the lentils and place them in a pot with vegetable broth. Bring to a boil, then reduce heat and simmer for about 20-25 minutes or until tender. Drain any excess liquid.

2. Sauté Vegetables: In a large skillet, heat olive oil over medium heat. Add diced onion, carrots, and celery, cooking until softened, about 5-7 minutes.

3. Add Garlic and Spices: Stir in the minced garlic, dried thyme, dried rosemary, and smoked paprika. Cook for an additional 1-2 minutes until fragrant.

4. Incorporate Mushrooms and Spinach: Add the chopped mushrooms and spinach to the skillet. Cook until the mushrooms are softened and the spinach is wilted, about 5 minutes.

5. Combine Mixtures: In a large bowl, combine the cooked lentils, sautéed vegetables, and soy sauce. Season with salt and pepper to taste.

6. Preheat Oven: Preheat your oven to 400°F (200°C).

7. Prepare Puff Pastry: Roll out the puff pastry on a lightly floured surface. Cut into a rectangle large enough to encase the filling.

8. Fill Pastry: Spoon the lentil mixture onto the center of the pastry, shaping it into a log. Fold over the pastry, sealing the edges to secure the filling.

9. Add Egg Wash: If using, beat the egg and brush it over the top of the pastry for a golden finish.

10. Bake: Place the prepared Wellington on a baking sheet lined with parchment paper. Bake in the preheated oven for 25-30 minutes, or until the pastry is golden brown.

11. Cool and Slice: Once baked, allow the Wellington to cool for 15-20 minutes before slicing. This will help the filling set and makes serving easier.