In a 5 quart saucepan, bring 4 cups chicken stock to a boil with 1 whole peeled carrot, 1 whole rib of celery and ½ bulb garlic whole (no need to peel). Once boiling, reduce heat to low and simmer, covered, for 30 mins.
2. Meanwhile, slice mushrooms into thin slices and cook in 5 tbs butter on low heat in a wide and deep sauté pan. Add salt and fresh ground pepper (to taste), garlic powder, and dry thyme. Cook for about 10 minutes, or until mushrooms have released most of their liquid and have decreased in size. Bring heat up to medium-high and add ½ cup white wine. Cook until wine evaporates, about 7 minutes.
3. Reduce heat on mushrooms to medium-low and slowly incorporate ¼ cup of flour, stirring for 2-3 minutes to cook out flour taste and develop flavor (mushrooms and flour should resemble a thick paste, and no flour bits should be visible).
4. Remove veggies and garlic from the hot stock and slowly whisk all of the stock into the mushroom/flour mixture, until well incorporated and no lumps are present.
5. Add Kitchen Bouquet, milk, more salt and fresh ground pepper (to taste), and poultry seasoning. Continue to cook over medium-low heat for about 20 minutes, stirring occasionally until gravy is thickened.
6. At this point, you could cool and refrigerate the gravy for up to 2 days in advance. You could also serve immediately. If adding pan dripping from a roast turkey or chicken, stir in and cook an additional 10-20 minutes, or until desired thickness.
Make about 1 quart of gravy, without drippings.