To make the dried quinoa and brown rice, place 3 cups of water in a medium pot. Add the rice and quinoa. Bring to a boil. Cover and let cook for 35 minutes. Strain any excess water and fluff with a fork.
Preheat the oven to 400ºF. Cut the acorn squash in half and remove the seeds. Lightly coat with olive oil and season with salt. Place cut-side down on a parchment-lined baking sheet and bake for about 35-40 minutes, or until the squash is pierced easily with a fork.
Meanwhile, make the filling. Heat the oil in a sauté pan over medium heat. Add the onions and cook until translucent, about 5 minutes. Add the mushrooms. Season with salt and pepper and saute until browned; 5 to 10 minutes. Add the minced garlic, Boku Super Shrooms, Boku Umami, and spices; cook for one more minute. Stir in the cooked brown rice, quinoa, and nuts. Taste and season with salt and pepper.
Once the squash is finished roasting, remove the acorn squash halves from the oven and fill each with the rice mixture. Grate vegan parmesan cheese over the top. Serve immediately and enjoy!