First cut the mushrooms, carrot and onion into slices and lightly sauté them in the bottom of a large stockpot with the vegetable oil for around 4 minutes
Add the water and the rest of the seasoning and allow the mixture to boil, and then let it simmer on low heat until it reduces.
You can use button mushrooms as a replacement for your assorted mushrooms as they will serve the same purpose.
But, you might wonder how to know when the broth is done. This is actually very simple: when all the vegetables are soft, and your stock has some mushroom flavor to it.
However, you will have to be patient as this can take up to one hour.
After the broth has taken the flavor and the vegetables are all soft, you can strain the ingredients out and what's left is a delicious vegan mushroom broth.