Plan: If cooking in an Instant Pot, make sure it's large enough to hold the roast, which is approx 9 inches long. I use this 6 quart model. If cooking in the oven, locate a high-sided baking dish that can hold the roast plus about an inch of broth, and that can be tightly covered with foil. Preheat oven to 375 degrees F (190 C).
Place vital wheat gluten in a large mixing bowl, and set aside. In a blender combine the beans, walnuts, garlic, onion powder, poultry seasoning, rosemary, sage, salt, pepper, 1 ½ cups broth (354 ml), vinegar, mustard, maple syrup, and liquid smoke. Blend on high speed until smooth.
Pour wet ingredients into vital wheat gluten, and stir until a dough forms. Move dough to a flat surface and knead by hand for 4 to 5 minutes. The dough will continue to firm up as you knead, and you'll see the gluten strands forming. *Alternatively, you can use a stand mixer with a dough hook attachment to do the kneading. Let it run on low (speed 2) for 3 to 4 minutes.
On a flat work surface use your hands to shape the dough into a log approximately 9 inches long x 3 ½ inches wide. Note, this will barely fit in a 6 Qt. Instant Pot; for the IP you can make it a bit shorter and wider if needed.
In a small bowl, combine the dry ingredients for the herb rub. Coat the outside of the roast with oil, then apply the rub. Let the seitan rest for a few minutes.
Cut a piece of cheesecloth large enough to wrap around the roast several times and with enough overhang on the ends to be securely folded underneath (the entire roast should be contained). Refer to photos above if needed. Wrap the roast, then tightly fold the ends underneath. Optional: wrap with 3 to 5 pieces of twine to create a "tied roast" appearance.
Instant Pot instructions: place trivet inside the insert, and add just enough of the remaining broth to reach the bottom of the trivet. Place wrapped roast on trivet, close and secure the lid. Cook on high pressure for 65 minutes. Allow pressure to naturally release for 10 minutes, then quick release remaining pressure. Carefully remove Instant Pot lid. Let roast cool for a few minutes, then lift out by trivet handles and place on counter to cool. Oven instructions: place wrapped roast in baking dish and add remaining 2 cups of broth. Flip the roast a couple of times so that the cheesecloth gets saturated with broth. Cover dish tightly with foil, crimping the edges. You want to contain as much of the steam as possible to keep the roast moist. Bake for 1 hour and 45 minutes, flipping the roast at the 1 hour mark.
To test for doneness, use tongs to press the center of the roast. It should feel very firm. It's okay if it feels slightly less firm than the ends, but if the center feels at all squishy, cook for another 5 minutes in the Instant Pot or 10 minutes in the oven. Remove the cheesecloth once cool enough to handle.
The roast can be served after cooling for about an hour, but the texture is best the next day. To store, remove the cheesecloth and allow roast to cool completely. Transfer to an airtight storage container, and refrigerate overnight.
If using for salads or sandwiches, the roast can be sliced and eaten cold. If serving as a whole roast, remove from refrigerator 1 hour before serving so that it can warm up. Then, pan-sear as described below.
Preheat a heavy skillet over medium heat. Add about a teaspoon of oil, and sear the top of the roast until browned, about 2 minutes. Flip the roast, and sear the underside. If desired, hold in place with tongs to sear the sides, as well. Place on a serving platter. Stir together the remaining 2 teaspoons of olive oil and the maple syrup. Brush onto the outside of the roast, and serve.