For the fillet, place beans, garlic powder, onion powder, paprika, salt, beet puree, 1 tablespoon mustard, maple syrup, and olive oil in a food processor and blend until smooth. Add vital wheat gluten and continue blending until a lump-free mixture forms. Knead the dough for 3-4 minutes, then shape it into a fillet.
Wrap the fillet in cheesecloth and simmer over low heat in vegetable broth for 90 minutes, turning it 2-3 times. Add more broth as needed to keep the fillet partially submerged. Remove the fillet from the broth, let it cool completely, then place it in an airtight container, refrigerate overnight and make the duxelles.
For the duxelles, finely chop mushrooms and tofu in a food processor. Heat a skillet over medium heat, add the vegan butter, and sauté the onion, garlic, and thyme for 5 minutes. Add the mushroom mixture, season with salt and pepper, and sauté for 15-20 minutes until golden-brown. Pour in white wine and cook for another 2-3 minutes. Remove from heat, let cool completely, then store in an airtight container in the refrigerator overnight.
The next day, brush the fillet with 2 tablespoon mustard and sear it on all sides in a hot skillet with a little vegetable oil. Set aside. Lay a piece of plastic wrap on a clean working surface and arrange slices of vegan prosciutto so they overlap slightly, forming a layer. Spread the duxelles over the prosciutto, smoothing it out with a spoon. Place the fillet on top, brush with the remaining 2 tablespoons of mustard, and roll it up. Chill the wrapped fillet briefly in the refrigerator.
On a clean surface, lay out a sheet of baking paper and roll out the puff pastry on it. Remove the fillet from the refrigerator, discard the plastic wrap, and place the fillet on the short edge of the puff pastry. Roll up the fillet in the puff pastry, pressing the seams tightly and trimming any excess. Brush the Wellington with soy cream, sprinkle with flaked salt, and bake in the center of the oven at 190°C (380°F) for 30-35 minutes.