Heat oil in a large skillet over medium heat.
Add garlic and spinach to skillet and saute until spinach is wilted and garlic is fragrant.
In a large bowl, add ricotta and egg. Whisk together until combined.
Add spinach mixture, cheeses, and Italian seasoning and stir to combine.
Scoop about 2 tablespoons of the cheese mixture, and stuff into each shell.
Pour ½ cup spaghetti sauce into the bottom of a 9"x13" baking dish and spread evenly.
Place stuffed shells in the dish and cover with remaining sauce.
Bake covered at 375 for 25 minutes.
Uncover, and bake for an additional 10-15 minutes.
Serve warm with crusty garlic bread and a green salad.
