In a skillet over medium-high heat, heat olive oil and add mushrooms to the pan. Sprinkle with salt and pepper and cook until the liquid in the pan is
gone. Add butter, reduce heat and stir until mushrooms are golden brown.

Once golden brown, add chopped onions for about five minutes. Remove the pan from the heat and add in garlic and stir for approximately 1 minute. Pour all ingredients into a bowl.

Add oats into the mushroom mixture, and then gently fold in the cheese. Add bread crumbs, parsley, and an egg to bind everything together. Add in Italian seasonings and mix until combined pressed together.

Cover the bowl with plastic wrap and put it in the fridge. Let sit for approximately 4 hours or overnight, depending on your preference.

Once chilled, preheat over to 450 degrees and line a baking sheet with parchment paper.

Mold mixture into balls with either your hands or a tablespoon. Place on parchment paper and bake 12-15 minutes.

After baking, bring pasta sauce to a boil and stir in meatballs until fully coated. Let simmer for about 45 minutes to an hour and then transfer to a bowl to serve.