Clean mushrooms, and gently remove stems.Mince ¼ cup yellow onion, mushroom stems, and 1 clove garlic
Heat skillet over low heat.Sauté onions and mushroom stems in 1 tablespoon olive oil until all the liquid has evaporated.Add garlic, and continue to sauté until the garlic is fragrant, about 1 minute.Remove from heat and allow to cool a little.
Puree ½ cup cottage cheese in a food processor until smooth.
In mixing bowl combine ¼ cup bread crumbs, cottage cheese, sautéd vegetables, ½ teaspoon parsley, and ¼ teaspoon nutritional yeast (optional).Season with salt and pepper.
Line baking pan with parchment paper (optional).Optionally lightly brush mushroom caps with olive oil.Stuff mushrooms and lay them out on the baking sheet.Bake at 400℉ for 15 minutes.