Boil the noodles according to the box directions, cooking them el dente
Preheat oven to 375°F
In a large bowl mix together all three cheeses, eggs and Italian seasoning.
In the bottom of a large casserole dish spread a thing layer of your sauce. (this will probably take about 1/2 of one jar)
Using a spoon fill each shell, I like mine pretty full but there is no wrong amount. I tend to do about two spoonfuls per shell
Place the filled shells in rows one at a time as you stuff them until your pan if filled
If you are using mushrooms I sprinkle them all over the tops of the shells
Top with your remaining sauce, you may want to use a little of a second jar. you want the shells pretty covered but not swimming
Sprinkle with mozzarella cheese
Cover with foil and bake for 30 minutes
Remove foil and continue to cook for 10-15 minutes, until the cheese is melted and bubbly