Place the neck, heart, liver, and gizzards of the turkey inside a medium size sauce pan. Cover the giblets completely with water and bring the water to a boil. Once boiling, simmer for 1 hour or until the meat is cooked through.
Next, use a slotted spoon to remove the giblets from the water and set them aside.
Once the giblets have cooled, remove the livers and discard them (they add a really strong taste and flavor not many people like). Use your fingers to remove any meat from the turkey neck. Add the meat to the rest of the giblets and discard what's left of the neck. Then dice the giblets into small pieces and reserve them for the gravy.
When you have taken your turkey out of the oven, pour the liquid and drippings from your turkey roasting pan into a large bowl. (Tip the pan away from your body and be careful not to burn your self)!
Now let the drippings sit for a minute, allowing the fat to naturally separate from the rest of the drippings. You will notice that the fat will rise to the top, leaving the drippings and liquid on the bottom. Use a large spoon or ladle to skim (remove) most of the fat from the top of the the drippings.
To make the gravy, use a large sauce pan and add 1 cup of drippings to the pan.
Add 1/2 cup flour to the pan and whisk together until it makes a smooth paste. (At this point, you'll need to use a little of your own judgement. You want a pasty consistency. If yours seems a little greasy, add more flour).
When you have found the right consistency, whisk the mixture slowly over the heat as it begins to brown. You are creating a roux.
Once you get a nice golden brown color, add 4 cups of chicken broth and 1 additional cup of drippings.
Allow the gravy to cook, whisking constantly for about 5 to 8 minutes, or until thickened. Then add the giblet meat
At this point, decide for yourself if you like the consistency of the gracy. If the gravy is too thick, add more broth or drippings liquid. If gravy is too thin, cook for about 10 minutes. If it's still thin, add a cornstarch slurry (mix 1 tablespoon of cornstarch with 1 tablespoon of water and then add to the gravy). Continue heating until gravy thickens to desired consistency.
Once your happy with the consistency of your gravy, season with salt and pepper, to taste, and enjoy!
Store leftover gravy covered, in the refrigerator.