Melt butter in a saucepan then add flour. Blend together until no lumps are visible. Add salt and pepper.
Cook and stir over medium heat for 5-10 minutes or until mixture starts to brown.
Disolve milk Powder in the stock.
Turn heat to low and slowly add broth, stirring constantly. Add thyme. Turn heat back up to medium and continue cooking and stirring until gravy boils and thickens. Adjust seasonings to taste.
Optionally, you can saute some mushrooms, and add them. Deglaze the pan with some cognac I also added some porchini powder...