Preheat your oven to 375°F (190°C).
In a large skillet, heat the olive oil over medium heat. Add the minced garlic and sauté for a minute until fragrant.
Add the vegan ground beef substitute to the skillet and cook until browned, breaking it up with a spatula.
Add the sliced mushrooms and chopped kale to the skillet and cook for another 5 minutes until the vegetables are tender.
Stir in the tomato paste and season with salt and pepper to taste. Cook for an additional 2 minutes to allow the flavors to meld together. Remove from heat.
In a blender or food processor, combine the soaked walnuts, garlic cloves, oat milk, and roux. Blend until smooth and creamy.
In a baking dish, spread a thin layer of the red sauce on the bottom. Place a layer of cooked lasagna noodles on top.
Spread a layer of the bechamel white sauce over the noodles, followed by another layer of the red sauce. Repeat this process until all the ingredients are used, finishing with a layer of the bechamel white sauce on top.
If desired, sprinkle vegan cheese on top of the lasagna.
Cover the baking dish with foil and bake in the preheated oven for 30 minutes. Remove the foil and bake for an additional 10 minutes until the top is golden and bubbly.
Allow the lasagna to cool for a few minutes before serving. Slice and enjoy!