1Heat butter in a pan and add the onion.
2Saute until onion is soft.
3Cut the button mushrooms into smaller pieces and add to pan.
4Cook until all of the butter has been absorbed.
5Add the chicken stock, milk and cream and bring to a boil.
6Simmer on medium heat for 10 Minutes.
7Add salt and pepper to taste.
8Add all of the ingredients to a blender and blend until smooth.