Gently rub the sage leaves between your fingers to release their natural oil.
Melt the butter with the sage leaves in a small saucepan over low heat. Let it melt slowly to extract the flavor.
Once the butter has melted, remove the sage leaves and discard them.
Next, increase the heat to medium and whisk in the chicken broth, poultry seasoning, garlic powder, and white pepper.
Simmer the marinade for 1-2 minutes until the ingredients are well incorporated.
Remove the pan from the heat and let it cool completely (about 30 minutes) before using.
Use a meat injector to draw some liquid into the syringe. Release excess air before injecting.
Inject about 3/4" into the turkey and release small bits of the sage-butter marinade into multiple spots.
Wipe away any spillage, place the turkey in a large pan, and refrigerate for 2- 8 hours.
Grill, smoke, or roast as directed.
Discard any additional marinade that has come into contact with raw meat.