Heat oil in a heavy bottom dutch oven over medium high heat.
Add turkey wings and brown until golden on each side making sure not to over load the pan, about 5-7 minutes. Remove from pan when browned.
Add onion, celery and carrots and sauté until they begin to caramelize, about 7 minutes.
While the vegetables caramelize, place fresh herbs, smashed garlic and peppercorns into the center of a cheese cloth. Roll it closed and tie the ends off to secure closed and form a sachet.
Add turkey wings, cheese cloth sachet and 12 cups of water into the pot. Bring to a light simmer and reduce heat to medium low.
Simmer for 1 ½ hours. Season with salt to taste if you want.
Cool and strain so that only the liquid remains. Refrigerate or freeze until you're ready to use.
Notes
Cool broth completely before putting in the refrigerator. This will last up to 5 days covered in the fridge and up to 6 months in the freezer.