Preheat oven to 350 degrees F (175 degrees C). In a large bowl, mix together ground chicken, mushrooms, Parmesan, basil leaves. Season with Italian-style seasoning, oregano, and garlic. Use your hands to combine well.

Divide mixture into balls about 1 1/2 inches in diameter. Place each ball into a hole of a muffin pan. Bake for 11 minutes, or until internal temperature reaches 160 degrees F (70 degrees C). Place marinara on a serving platter and place meatballs on top. Garnish with shredded Parmesan and fresh oregano if desired.