Preheat oven to 400ºF and grease a 9x13 baking dish; set aside.
In a skillet over medium heat, cook hot Italian sausage, breaking it into small pieces. Remove with a slotted spoon and transfer to a bowl; set aside.
To the skillet, add onions, peppers and carrots; sauté for 5 minutes. Add garlic and sauté for 1 minute. Add crushed tomatoes, corn, red wine, brown sugar, basil, oregano, red pepper flakes, salt and pepper. Stir very well, reduce the heat to medium-low and gently simmer while stuffing the pasta shells.
Fill up a large bowl with very hot water from the tap (not boiling water) and add half of the pasta shells to it. Let them sit until softened, about 15 minutes.
When ready to stuff, drain them, fill up the bowl with very hot water again and add the other half while stuffing the first batch.
In a medium bowl, combine sausage, spinach, ricotta and asiago; stir until combined.
Spoon half of the tomato sauce in the prepared baking dish.
Stuff soaked pasta shells with Italian mixture and place them in the prepared dish over the sauce.
When all the shells are stuffed, spoon the remaining sauce over the stuffed pasta shells and sprinkle with parmesan cheese.
Transfer to the preheated oven and bake for 30 minutes or until heated through and the sauce is bubbling.
Remove from the heat and let it sit for 5 minutes before sprinkling on some fresh chopped parsley.