Cover the bottom of a large heavy stock pot with oil and heat to medium. Working in batches, one layer at a time, brown the turkey pieces on all sides. Do not use turkey liver which tends to make stock bitter. Remove pieces to a bowl as they brown. After browning the turkey, add onion, carrot, and celery, leaves included, and cook until softened (about 10 minutes), scraping up the browned bits in the bottom of the pot. 

Return the turkey to the pot and cover by 3-4 inches of cold water. Bring to a simmer and cook, skimming off the foam as it rises, until there's no more (or very little) to skim. Add the chopped fresh parsley, thyme, peppercorns, and bay leaves. 

Reduce the heat to low and simmer AT LEAST 2 hours; I let mine go all night. Add more water as necessary to keep the bones covered; at a very low simmer it will be fine all night. BONUS: your house smells like Thanksgiving by the time you get up.

Cool it for a half hour or so, and strain through a big colander lined with cheese cloth. Skim off any yellow fat that rises to the surface. You can strip the meat off the necks and use in stuffing or dressing, but there's not much flavor left; it adds a little texture.

If I have room, I keep the strained pot of stock on a back burner over very low heat. If not, it’s just off to the side, and I add a ladle of stock to my green beans, to the water I use to boil potatoes in, the bread stuffing I make, and of course I use it to baste the turkey and it's the base of the gravy.

Turkey stock may be made up to 3 days in advance, cooled, covered, and refrigerated. It may be frozen in airtight containers for up to 3 months.

Cook’s treat:  ladle a bowl full and add just a titch of salt and taste, wondrous. 

Note: Do not add salt to the broth; rather, season the dishes you use the broth in as you go. If there's any stock left over, use it to start the stock you'll make from your turkey carcass.

Tip: if you have a multi-purpose stock pot that includes a pasta strainer insert, use it! It will make straining the stock much easier.