Heat 2 tablespoons of olive oil in a large skillet over medium heat. Add 1 cup of chopped onions and 3 cloves of minced garlic, stirring frequently for about 5 minutes until soft and fragrant.

Mix in 2 cups of chopped mushrooms into the skillet and sauté for another 7-10 minutes. Add 2 cups of fresh spinach, stirring occasionally until it wilts down, about 2 minutes.

Remove the skillet from heat and transfer the mixture to a large bowl. Stir in 1 cup of cooked lentils, 1 teaspoon of dried thyme, 1 teaspoon of smoked paprika, 2 tablespoons of soy sauce, 2 tablespoons of nutritional yeast, 1 teaspoon of salt, and ½ teaspoon of pepper. Let it cool for a few minutes.

Preheat the oven to 400°F (200°C). Roll out your sheet of puff pastry into a rectangle on a floured surface.

Spoon the filling mixture into the center of the rolled pastry, ensuring to leave space on each side for folding. Fold the pastry over the filling, creating a parcel with the seam on the bottom.

Transfer the sealed Wellington seam-side down onto a baking sheet lined with parchment paper. Brush the top with the plant-based egg wash and sprinkle sesame or poppy seeds on top.

Bake for 25-30 minutes, or until the pastry is golden brown and puffed. Let it cool for a few minutes before slicing.