Combine 8 c stock in the pot with the mushrooms, onions, garlic, soy sauce, and bay leaves and bring to a simmer.
Meanwhile, combine remaining c stock with gluten and cream. Knead until well mixed.
Squeeze out excess liquid and cut the dough into 2-4 pieces.*
Form each into a ball, then flatten into a disk.
Lightly flour the counter and rolling pin and roll out each piece of dough as thin as possible – about ¼ inch.
When the broth is simmering, carefully add the seitan. Cover and simmer for an hour, flipping the pieces over every 10-15 minutes.
Let cool and then use in your favorite "beef" recipe, or store with any remaining broth in the refrigerator. It will keep for 4-5 days.