Every post seems to do them slightly differently, but basically, shotgun shells are typically made by stuffing pasta tubes with flavorful fillings, wrapping them in bacon, and then cooking them to crispy perfection.
At least one of my sources suggested cooking the noodles (manicotti) for 4 or 5 minutes before hand.
Most others I saw suggested not doing that.
For my first attempt, I decided to pretty much follow Hey Grill Hey's recipe, and she did suggest pre-cooking the noodles.
