Heat your oil, over medium heat.Saute for about 6 minutes, add in the onions and garlic and continue to cook, stirring often, until the liquid is gone.Season with salt and pepper.Add in the butter and cook until the mixture begins to brown. The darker brown the mushrooms become, the richer tasting they will be.Remove from heat and add in the Mozzarella. Allow the mixture to cool for 15 minutes or so.Add in the parsley and ¾ of the breadcrumbs, stir to combine.Mix in the egg.Season a bit more with Salt & pepper and if you like a bit of heat some Cayenne pepper.If mixture still looks wet, add in another ¼ cup of breadcrumbs.Refrigerate at least 1 hour and up to overnight.The flavors will mingle and the consistency will be better for the balls.When ready to cook, preheat your oven to 350 degrees and form into meatball shape.It's OK if they seem moist, they will hold together.Heat some grapeseed or olive oil in a non-stick frying pan and brown your mushroom. You want them crispy...yet not burnt.Transfer to the oven and cook for 15 minutes.Serve them with Jar Goods Sauce (we love them with the Classic Spicy Sauce) on their own, topped with some fresh Parmesan cheese, with pasta or on a roll with some greens. Yummmm!