Heat the butter in a sauce pan and sweat the onion. Make sure they don't brown. 将黄油在炒锅中融化，加入洋葱煸炒出香味，注意不要炒出焦黄色。
Add the flour and make a blond roux. 加入面粉用手持打蛋器打圈划出金色面糊。
Add the chicken stock and bring to a boil. Allow the sauce to simmer for 30 minutes. 加入鸡高汤烧开，将火关小慢煮30分钟。
Strain through a chinois. 用细目漏勺过滤。