Melt butter in a saucepan on low heat. Once melted, add in minced garlic and a rosemary sprig. Heat and infuse garlic and rosemary for a few minutes, but do not overcook or brown.
Add in 2 cups of broth and the white wine, and bring to a low boil.
Remove rosemary sprig. Gradually add the flour, whisking constantly around the pan, until the gravy is lightly golden.
Bring to a boil and slowly add in 2 more cups of stock. Bring to a boil.
Continue whisking until the gravy has thickened to your liking, about 8 to 10 minutes.
Remove from heat and salt and pepper to taste.
Serve immediately or cool and store if making in advance.
* If made in advance: Turkey pan juices can be added on the day you reheat/serve.