Place the turkey bones in a large stock pot and cover with cold water. Slowly bring to a simmer, using a ladle to skim off any impurities that rise to the surface.
Meanwhile, cut the onion, celery and carrot into a large dice and set them aside with the garlic bulb, bay leaves and peppercorns. Wrap the celery leaves, rosemary, thyme and parsley in the leek and tie it tightly with the kitchen twine.
Once the broth has come to a simmer add the vegetables, spices and herb bundle, return to a gentle simmer, continually removing any impurities and cook gently for 4 hours.
Strain the stock through a mesh strainer lined with damp cheesecloth; cover and refrigerate for 4-5 days, or freeze in airtight containers up to one month.