Combine sunflower seeds, nutritional yeast, sesame seeds, garlic powder, and salt in a food processor or good quality blender until they’re ground into a finely grated mixture like parmesan cheese. You may also use something smaller, like a bullet blender, to make the vegan parmesan cheese. Taste the mixture and add any extra yeast, salt, or flavorings you’d like. You may need to scrape down your blender and blend the mixture multiple times to ensure no chunky pieces of sunflower seeds are left behind.
Add the vegan parmesan cheese to a large mixing bowl. Stir tahini, the first amount of olive oil, minced garlic, italian seasoning, and chopped chives into the parmesan mixture. The final combination will be a pasty mixture. Prepare medium and large-sized cremini mushrooms caps by removing the stems and arranging them on a sheet tray lined with parchment paper.
Preheat an oven to 350 degrees. Fill each mushroom cap with about 2 teaspoons of parmesan filling. You can gently pack the filling down so it densely fills the mushroom caps. It’s okay if some filling rises above the mushrooms too. Drizzle approximately ¼ teaspoon of olive oil over the top of each piece.
Bake the tray of mushrooms for 35 minutes or until done. The top of the parmesan filling will be lightly golden with a slight crust. The mushrooms should be tender for biting but still have their integrity. Allow them to cool for 5 minutes before enjoying. Store fully cooled stuffed mushrooms in your refrigerator in an airtight container.