Heat olive oil in a skillet over medium high heat; dd wings and onions and cook, flipping wings and stirring onions occasionally, until golden brown, about 10 minutes Add garlic, thyme and rosemary sprigs; add 1 ½ cups or 350ml stock to skillet and stir, scraping up any brown bits on the bottom of the pan

Transfer to a small stock pot

Stir in remaining broth, carrot, celery and bay leaf; bring to a boil

Reduce heat to medium-low and simmer for about 1 hour, skimming occasionally

While broth is simmering, puree roasted onions and about ½ cup or 125ml pan juices from turkey (after roasting your turkey) in blender or food processor

Transfer to a large saucepan

Remove and discard wings

Strain broth through a large strainer into saucepan with onions

Press on vegetables in strainer to extract any remaining liquid; discard strained vegetables

Bring strained broth and onions to a gentle boil, stirring occasionally

Stir in the butter and season with salt and pepper