Take your pastry puff sheets out of the freezer about 40 minutes before making your sausage rolls and allow them to warm up and become pliable.
Preheat your oven to 375° F (190° C).
Mix 2 tablespoons ground flax seeds and 4 tablespoons water together and set aside to get thick and sticky.
Peel and finely chop a small onion and add it to 2 tablespoons of cooking oil. Sprinkle with a little salt and cook over low heat for about 5 minutes until they become translucent.
Add water, soy sauce, oregano, fennel seeds, and cayenne to the onions and bring to a boil.
As soon as it starts to boil, turn off the heat and add TVP, mix well and cover for 5 minutes to allow the TVP to soak up all of the broth.
Add your flax mixture and chopped fresh parsley then stir well.
Lay your pastry puff sheets flat and cut along the fold lines so that each of the 2 sheets is cut into 3 long pieces.
Form a long tube of sausage down the center of each pastry puff sheet.
Brush one long edge with aquafaba, then take the opposite side and fold it over the sausage filling and press it onto the brushed edge.
Use your fingers to press the edge together and seal in the sausage.
Cut the sausage rolls into the desired sizes. (I usually cut them about 1 1/2 inches long for appetizer-sized pieces.) Remember they will puff up a lot when they are baked.
Cut a small slice in the top of each sausage roll and brush the tops with aquafaba.
Arrange on a parchment-lined baking sheet about 1 inch apart and bake at 375° F (190° C) for 25 minutes until they are puffed up and golden brown.
Notes
Allow your pastry puff to warm up until it becomes soft and workable.
Don't overfill your rolls are they will be difficult to close up. You want a line of sausage about 3/4 inch wide and high in the center of your pastry puff strip.
If you don't have aquafaba, you can use water to seal the rolls together, and you don't need to brush the tops.