The seitan starts with my basic method that can be found here on my website and in my book Vegan Pressure Cooking. I use beef-style seasoning and Catanzaro herbs for a rustic, meaty flavor.
Combine the first six ingredients in a medium bowl (or a stand mixer bowl).
Whisk together the first set of wet ingredients (NOT the cooking broth) in a small bowl.
Pull dough apart (or slice into two roasts. Set aside.
Remove cutlets from the broth to cool before handling or serving. Reserve the cook broth for storage.
Wrap both seitan roasts in parchment paper, place in a sealed plastic bag and freeze for 3 hours. After 3 hours use a mandoline slicer, food processor or sharp knife to thinly slice the seitan. Store the seitan in the cook broth in an airtight container. Stores well in the refrigerator 3 to 4 days and in the freezer up to 3 months.
Heat extra-virgin olive oil in large saucepan or soup pot on medium high. Cut the onions into half-moon slices (about 3 cups). Add to the pot, sprinkle with sugar and saute on medium-high to high heat until slightly browned (about 10 minutes, stir frequently, add water or vegetable broth, if necessary, to avoid sticking).
Add the beef-style broth, Worcestershire sauce, and red miso. Bring to a boil. Pour 1 1/2 cups of broth into a skillet and set aside. Cover the pot with a lid, reduce heat to low and simmer for 10 to 15 minutes.
Meanwhile, bring the broth in the skillet to a boil. Add the shaved seitan 3 1/2 to 4 cups to the skillet. Return to a boil. Cover, reduce heat to low and simmer for 10 to 15 minutes.
While the broth and seitan and simmering, combine the sour cream and horseradish in a small bowl. Set aside
Using a slotted spoon, transfer seitan to a colander to drain some of the cook broth. Pour remaining broth from the skillet back into the soup pot. Set aside.
Toast the hoagie rolls by slicing them and setting them over the top of the toaster for just under a minute (long enough to lightly brown). Spread horseradish cream over the hoagie rolls. Layer about 1/2 to 3/4 cup seitan onto each roll. Repeat to make 5 or 6 sandwiches.
Pour broth from the soup pot into 5 or 6 small bowls (for dipping) and place on each plate.