Spray a pan with olive oil cooking spray, saute onion until soft. Add turkey sausage and brown until cooked through. Add garlic and cook for an additional minute. Remove from heat. Discard seeds from the squash and use a fork to remove your "spaghetti." To remove excess moisture from the squash, place it in a clean kitchen towel and give it a squeeze. Then season the squash with a little salt and pepper. Stir an egg, parmesan cheese, and a sprinkle of pepper into the ricotta. Preheat your oven to 375. Spray a casserole dish with a olive oil cooking spray and begin the layering process. First, spoon about half of your sauce on the bottom of the casserole dish. Next, add the cooked sausage. Layer spaghetti squash over the sausage then add the rest of the sauce and some fresh chopped basil. Finally, top sauce with the ricotta cheese mixture and then add the shredded mozzarella. Bake until cheese is melty and bubbly - about 15-20 mins. To brown the cheese, broil on low for 5-10 minutes at the end, but watch carefully. It sneaks up on you! Remove from oven and let sit for a few minutes. If there is excess water at the bottom of your pan, you can carefully try to drain it out from the corner of the pan or serve with a slotted spoon. Garnish with fresh basil before serving!