Preheat your oven to 350° F.
Wipe mushrooms clean and pull out the stems and chop finely and set aside
Toss the mushrooms with olive oil, balsamic vinegar, salt, and pepper.
Spread out on a sheet pan and bake for 30 minutes
Flip the mushrooms over and let them drain and cool
Sautee the onions and crumble the sausage in a heated pan and sauté until golden brown. Break up into small pieces while the sausage is cooking. Add the garlic, kale, and mushroom stems and cook until the greens are wilted.
Drain, set aside and cool.
Mix the sausage mixture with the cream cheese, Parmesan and mix well with your hands. Break apart any large pieces of sausage.
Heat your oven to 375° F. Line up your mushrooms in a greased baking dish with the core side facing up. Stuff each mushroom with a generous portion of the creamy sausage mixture.
Bake your mushrooms for roughly 35 minutes or until the cheese on top is golden brown.