Preheat the oven to 350℉/176℃ and line a baking sheet with parchment paper.
Use a paring knife to carefully remove the mushroom stems, finely chop them, and set aside. Then use a small spoon to gently scrape out the gills and discard.
Place the mushrooms hollow side down on your tray and bake for 10 minutes. Remove them from the oven and use a clean dish towel or paper towel to absorb the excess moisture that the mushrooms release during baking. (Dry the parchment paper too.) Then flip them hollow side up and set them aside.
Meanwhile, add the onion, garlic and chopped mushroom stems to a large pan and sprinkle with salt and pepper. Dry sauté for about 5 minutes (the mushrooms will release moisture so you won't need oil) until softened and reduced. Then add the rice and mix well, cooking/toasting for about 30 seconds.
Add approx. ½ cup of broth to your pan, stirring often until absorbed. Continue adding broth about ½ cup at a time, stirring your risotto often. Wait until the liquids are absorbed before adding the next portion of broth. Repeat until all 3 cups of broth are used. This will take around 20 minutes. Then remove the pan from the heat, and stir in the cranberries.
Increase the oven temperature to 400℉/204℃. Then, generously stuff the mushrooms, sprinkle with vegan Parmesan cheese, and bake for 15 minutes.
Notes
Use caution when removing your mushroom stems. Don't rush, especially if it's your first time making stuffed mushrooms.
If it's your first time making stuffed mushrooms, buy a few extra, just in case some break. Then, if you do end up with a couple of broken ones, finely chop them and add them to your stuffing. No waste.
Dry the excess liquid after the first round of baking your mushrooms. Don't skip this step.
Do NOT add all the broth at once, to your pan of arborio rice. When making Italian risotto, the slow way, is the best way for a perfectly creamy texture (without adding creams, vegan butter, or vegan cream cheese).
Leftovers will keep in the refrigerator for 2-3 days in a sealed container.