Basle flour soup is a type of Swiss soup that is made with a roux of flour and butter, and then typically has vegetables, meat, and/or cheese added to it.
Melt the butter (moderate heat) and, stirring constantly, cook the flour to a chestnut brown. Remove the pan from the heat, add the warmed stock, mix well and simmer without a lid on a low heat for 45 minutes. Season with ground nutmeg and pepper. Serve with grated cheeese.