For the seitan, put the flour and water in a bowl.
Knead for 10 minutes to a firm dough. (A food processor with a dough hook is advantageous here). After the 10 minutes, cover the seitan with lukewarm water and let it sit for 30 minutes.
Finely chop the onion and garlic and sauté in the oil in a large pot. Pour in the vegetable broth and add the remaining spices. Remove the broth from the heat.
After 30 minutes, knead the dough well. It is best to do this by hand, otherwise you will have flour water all over the kitchen. The dough will break down a bit during this process. Drain the milky liquid through a sieve, cover the dough again with lukewarm water and knead again. Repeat this process (about 4-5 times) until the dough has taken on a spongy but compact consistency and the water is only slightly cloudy. At this point, the dough will have shrunk into a small lump. But don’t despair, it will rise again to about 3 times that size when cooked.
Rinse the seitan well, squeeze it out and cut it into pieces of any size (depending on its later useà nuggets, cutlets, sliced meat,…). Bring the broth to a boil and boil the seitan pieces vigorously for 10 minutes. Reduce the heat and simmer for another 30 minutes.
Pour the seitan into well-sealed containers (e.g.: large canning jars) and cover with the broth.
Let the seitan steep in the broth in the icebox for another 2 days before use.