Set the puff pastry out to thaw.
In a medium-sized pot, saute the carrots and celery in the vegan butter/oil or vegetable stock until tender.
Add in the lentils, water, bouillon, onion powder, garlic powder, vegan Worcestershire sauce, paprika, sage, thyme, and pepper.
Bring to a boil then reduce to a simmer for 15-20 minutes, or until the lentils are tender and have absorbed the liquid. Add some salt or soy sauce if needed.
Turn off the heat, but leave the pot on the burner. Stir in the kale and sunflower seeds. Cover the pot for about 5 minutes, or until the kale has wilted.
Mix in the breadcrumbs. Let the lentil mixture cool until just warm, no longer hot.
Pre-heat the oven to 400F degrees.
Once the puff pastry is thawed and pliable, you can start assembling your vegan wellington.
Scoop the lentil mixture in the center third of the puff pastry in the shape of a log. Leave an inch of room on the edges. Make sure it's packed tightly.
Fold the sides of the puff pastry over the top of the lentil mixture, tightly. There should be about a half an inch of overlap. Pinch, seal and tuck the edges. Use water to help create a more secure seal.
Cover a baking sheet with parchment paper or a silicone baking mat. Place the wellington on it, seam-side down.
Score the pastry (directions in the post above) and then brush with the non-dairy milk (this will create a golden crust as an egg wash would.)
Bake for 30 minutes, or until golden brown.
Let cool for about 5 minutes, then use a serrated knife to cut slices.