Put the puff pastry out to thaw. In a medium-sized pot, saute the celery and carrots at the vegan butter/oil or vegetable stock till tender.
Add the water, lentils, onion powder, bouillon, garlic powder, vegan Worcestershire sauce, sage, thyme, paprika and pepper.
Bring to a boil then reduce to a simmer for 15-20 minutes, or till the lentils are tender and have absorbed the liquid. Add some salt or soy sauce if necessary.
Switch off the heat, but leave the pot on the burner. Stir in the kale and sunflower seeds. Cover the kettle for 5 minutes, or till the kale has wilted.
Mix in the breadcrumbs. Allow the lentil mixture cool till just warm, no more hot. Then pre-heat the oven to 400°F.
When the puff pastry is pliable and thawed , you can begin building your vegan wellington.
Scoop the lentil mix in the middle third of this puff pastry in the form of a log. Leave an inch of space on the edges and make certain it's packed tightly.
Fold the sides of the puff pastry over the top of the lentil mix, closely. There ought to be approximately a half an inch of overlap. Pinch, seal and tuck the edges. Use water to help make a more secure seal.
Cover a baking sheet with parchment-paper or a silicone baking mat. Put the wellington onto it, seam-side down.
Score the pastry and then brush with all the non-dairy milk (that will make a gold crust as a egg wash could.)
Bake for half an hour, or till golden brown. Let cool for 5 minutes, then use a serrated knife to cut pieces.