You’ll need a large heavy-based pot – ideally an enamelled cast-iron casserole dish.
Heat 1 tbsp oil in your large pot and place over high heat. Add the mushrooms or seitan/quorn pieces and sear in the pan until golden on all sides. Scoop them out and set aside.
Turn heat down to medium, then add the onions, carrots and celery to the same pot. You might need to add a bit more oil. Let the veg sweat down. Just as they are beginning to colour add the garlic.
After about 30 seconds add the flour. Stir it so everything gets coated. Let it cook for a minute or two.
Pour in the Guinness slowly, stirring as you go. Give it another really good stir to work out most of the lumps. Don't worry about any small lumps.
Add the potatoes, swede, veg stock, soy sauce, salt, pepper, sugar and herbs and give it a good stir. Bring slowly to a boil, stirring frequently. Then immediately turn down to medium-low.
Let the stew simmer uncovered, stirring occasionally until the potatoes are soft and the gravy is thick. It will take about 45-50 minutes.
About 10 minutes before you are going to serve, add the mushrooms or seitan/quorn pieces back in and give it a stir.
Serve with bread and some cooked greens on the side.
