Preheat oven to 450 degrees F.
Cook the onions in a large skillet with oil over medium-high heat for 3-4 minutes or until translucent.
Stir in the garlic and red crushed pepper, cook for an additional 20 seconds.
Add the vodka and let it reduce by half.
Add the crushed tomatoes and season with salt, pepper, oregano, and sugar.
Reduce the heat to low, cover, and cook for 20 minutes.
Stir in the heavy cream and check for seasoning.
In a large bowl, combine the ricotta cheese, spinach, mozzarella cheese, parmesan cheese, granulated garlic, salt, pepper, and egg.
Add 1 cup of sauce to the bottom of a baking dish.
Stuff cooked shells with ricotta mixture and place them in the baking dish.
Pour the remaining sauce over the stuffed shells.
Cover with mozzarella and parmesan cheese and bake for 15 minutes.
Enjoy!