In a large pot of salted boiling water, cook the Jumbo pasta shells per instructions on package for Al Dente. Drain and set aside.
In a skillet add 1 TBS cooking oil and heat up. Place onions in and cook until softened and a little brown. Add in sausage, break up and brown thoroughly. Turn off burner and drain any excess grease. Stir in spinach,, 2 cups of shredded cheese, salt & pepper. Let cool while making the creamy sauce.
To make the creamy sauce, melt 4 TBS butter in medium pot over medium heat. Whisk in flour for 1-2 minutes until combined. Slowly stir in milk a little at a time until smooth. Cook an additional 2-5 minutes until mixture thickens into a gravy consistency. Turn off burner. Add in parmesan cheese and mix to combine. Season with salt & pepper, if needed.
In the bottom of a 9 x 13 baking dish spoon enough sauce in and spread to coat the bottom and sides of baking dish. (This will keep the shells from sticking.) Place 2 TBS of sausage mixture into a cooked shell and place into the prepared baking dish. Complete all shells. Pour creamy white sauce over all the stuffed shells and sides of dish. Sprinkle with dried parsley.
Bake in preheated oven for 30 minutes until cheese is melted and sauce is bubbly. Enjoy.
