Heat 2 Tbsp in a large, deep pan over medium-high heat. Add onions and mushrooms and cook for 4-5 minutes until softened.
Add turkey and sausage and cook, breaking up the meat, until it is cooked through. Add the sauce and stir to combine.
Add the water and the pasta shells and bring mixture to a boil. Reduce heat to bring mixture to a simmer and cook for 15-20 minutes, stirring often until pasta is cooked al dente.
Meanwhile, combine riccota cheese, 1/2 cup parmesan, and 1 Tbsp dried parsley. When pasta is done cooking, spoon dollops of the cheese around the top and use the back of a spoon to spread it out.
Top with additional parsley and parmesan cheese if desired.