In a medium saucepan, melt the butter. Add the flour and whisk until well combined. Cook the roux until it turns a blond color.
Slowly add the stock, a little at a time. Before adding more stock, whisk and let it come back to a gentle boil each time. if you've reached a silky-smooth consistency, add the stock.
Add salt and white pepper to taste. Depending on how soon you plan to use it, you may need to loosen up the sauce a bit with a little hot stock before using it. Enjoy this sauce with your favorite dishes.