Bring 4-5 litres of water to the boil in a large pasta pot. Add pasta, stir to separate and cook for 10-12 minutes or until pasta is tender. Drain well and place in a large mixing bowl.
Heat oil in a large pan over high heat. Add the sausage pieces to the pan and cook for 3-4 minutes or until golden and cooked through. Remove and set aside. Add mushrooms to pan and cook over high heat until cooked, about 3-4 minutes. Set aside with sausages.
Reduce heat and add butter to pan. Add onion and garlic and cook gently for 2-3 minutes or until softenened. Add the semi dried tomatoes, water or stock. Return sausage and mushrooms to pan, with pasta, tomato sauce and spring onions. Toss well to combine then transfer half the mixture to a large well-greased baking dish (approximately 2 litre capacity).
Dollop ricotta over pasta then top with the remaining sausage mixture and scatter with parmesan cheese.