01 - Preheat oven to 400°F. Line a baking sheet with parchment paper.
02 - Heat 2 tablespoons olive oil in a skillet over medium heat. Add chopped mushrooms and onion. Sauté for 6-8 minutes until softened and moisture evaporates. Stir in garlic and cook 1 minute more. Remove from heat and cool slightly.
03 - In a large bowl, combine ricotta, cooled mushroom mixture, breadcrumbs, Parmesan, parsley, oregano, egg, salt, and pepper. Mix until well combined.
04 - Shape mixture into 16-18 golf ball-sized meatballs. Place on prepared baking sheet. Bake for 18-20 minutes, turning once halfway, until golden and set.
05 - Heat 2 tablespoons olive oil in a saucepan over medium heat. Add onion and cook 4 minutes until translucent. Add garlic and cook 1 minute.
06 - Stir in crushed tomatoes, basil, oregano, sugar, salt, and pepper. Simmer uncovered for 15-20 minutes, stirring occasionally, until slightly thickened.
07 - Gently transfer baked meatballs to the sauce. Simmer together for 5 minutes to meld flavors.
08 - Serve hot, garnished with fresh basil and extra Parmesan. Pair with spaghetti, polenta, or crusty bread.