Add the vegetable broth and dried mushrooms to a pot. Season to taste, lightly, with salt and pepper. Bring the pot to a boil, then reduce to a bare simmer. The pot will stay on the heat for the entire process, so make sure the simmer is very slight so the broth doesn't evaporate.
While the broth simmers, heat the olive oil in a large skillet over medium-high heat. Add the sliced cremini mushrooms with a pinch of salt and pepper. Cook for 3-4 minutes, stirring often until the mushrooms start to brown. Add the onion and stir.
Use a slotted spoon to scoop the reconstituted mushrooms from the broth and transfer them to the skillet with the cremini mushrooms. Once you start to see brown bits gathering on the bottom of the skillet, scoop a few tbsp of broth into the skillet and scrape up the bits.
Repeat, letting the brown bits accumulate in the pan, adding a few tbsp of broth, scraping, and stirring until your mushrooms and onion are deeply browned and caramelized. About 10 minutes. Remove about 1/3 of the mixture and set it aside in a bowl.
Add the garlic to the skillet and cook for about 30 seconds, until fragrant, then add the rice and reduce the heat to medium-low. Toast it for about one minute before adding about a 1/2 cup scoop of the hot stock and the white wine vinegar. Stir and cook until the liquid has been absorbed.
Add about 1 cup of the stock and cook, stirring often, over a medium bubble (adjust the heat between medium-low and medium as needed), until completely absorbed. Repeat this step until the rice is fully cooked through. This process will take about 30 minutes.
Stir in the vegan cheese and vegan butter. You can reheat the reserved mushrooms in a skillet or the microwave before scooping over the risotto to serve.