Defrost puff pastry and set aside. Preheat oven to 375℉ (190℃).
In a food processor or high powered blender mix together half mushrooms, onion, and garlic. You may have to add some water to get it going. add in a few tablespoons at a time, and no more than what is needed.
Roughly chop the other mushrooms and set aside.
Once mushrooms and onions are minced together, add in the rest of the ingredients, minus the olive oil (vital wheat gluten, egg, fennel seeds, dried ground sage, salt, pepper, paprika, thyme, oregano, vegetable bouillon, and nutritional yeast).
In a large frying pan heat up the olive oil on medium high heat. Add in the minced mushrooms and sauté for 3 minutes.
Add in the blended mixture, lower the heat to medium low and sauté until all the water has evaporated and the mixture begins to thicken. This should take between 10-15 minutes, depending on how much moisture there is in the mushrooms and how much water was added for blending.
While the mixture is sautéing, roll out the puff pastry until it is about half its original size. Make sure to flour the bottom, and add flour as needed to prevent it from sticking to the counter and rolling pin.
Once the mushrooms have begun to thicken, remove it from the heat and allow to cool until it is workable. Make sure that it is cool enough that you can touch it and also cool enough not to melt the oil in the puff pastry.
When cooled place the mixture in inch (2 cm) wide lines down the pastry. Make sure the lines are at least 2 inches (4 cm) apart from each other.
Once you have placed all the mixture down, cut the puff pastry in between the lines of mushroom.
Gently cover the mushroom with the puff pastry and seal the sides.
Place the logs seam side down into a lined baking dish. Lightly brush some olive oil, or egg wash on top of the logs, and then you can optionally sprinkle with sesame seeds or any dried herbs you want.
Cook for 40 minutes at 375℉ (190℃), or until golden brown.
Remove from oven and allow to cool slightly before cutting into bite-sized pieces and serving.