This gravy would be best made with fresh stock from a cooked chicken or turkey, but good store-bought stock can be used if needed. Try to pick a flavorful, low sodium stock because this will reduce and the salt could become overwhelming. Wait until the gravy is reduced to add substantial amounts of seasoning as the flavor will change while it cooks.
8 Tbsp unsalted butter
7 cups turkey or chicken stock
1 cup dry white wine (I used Chardonnay)
1/2 cup flour
1 1/2 Tbsp cornstarch
1 bay leaf
2 springs rosemary, bruised
4 dried porcini mushrooms
Melt butter over medium heat in a large saucepan. Whisk in the flour and continue whisking until smooth, golden brown, and aromatic, about 4 minutes.
Raise the heat to medium-high and slowly pour in 1/2 cup of wine while whisking. The mixture will bubble and thicken. Add the stock in a slow, but steady stream, whisking constantly. Bring to a boil, stirring periodically, then lower the temperature while keeping a steady boil.
Add in the bay leaf, rosemary, and mushrooms. Continue to cook until reduced by 1/3. In a small bowl, mix the cornstarch with a few teaspoons of COLD water. Add this to the broth while stirring and continue to stir as the gravy thickens. Also stir in the remaining 1/2 cup wine.
Continue to cook until desired thickness is achieved; it will continue to thicken as it cools. Adjust seasonings to taste.