Preheat the oven to 375 degrees F and line a baking tray with parchment paper.
Using a paring knife, carefully remove the mushrooms stems, finely chop them, and set aside. Then using a small spoon, carefully scrape out the gills and discard.
Place the mushrooms hollow side down on your tray and brush the tops with your olive oil using a silicone brush. Bake for 10 minutes and then using a paper towel, absorb any excess moisture that the mushrooms released during baking, and flip them hollow side up. Set aside.
Meanwhile, start preparing your stuffing by adding the cooking oil, onion and chopped mushroom stems to a large skillet. Cook over medium heat for about 5 minutes until softened and reduced. Then add your garlic, salt and pepper and give it a stir. Then add the rice and mix well until rice is coated with the oil.
Next you will add 1/2 cup of your vegetable broth to the skillet, stirring often until absorbed. Continue adding 1/2 cup at a time, stirring your risotto often. Wait until the liquids are absorbed before adding the next portion of broth. Continue doing so until all 4 cups of broth are used. This process should take around 20-25 minutes. Remove from the heat and add your cranberries and mix to combine.
Turn up the heat of your oven to 425 degrees F. Then, divide your stuffing mixture between your mushrooms. You want your mushrooms heaping with the stuffing. Then sprinkle the stuffed mushrooms with Parmesan cheese if using and bake for 15 minutes. Serve warm.
Vegan Parmesan Cheese (optional)
Add all the ingredients to a food processor and process until a fine meal is achieved.