Beat the egg whites until they are foamy (see Tips below for notes on the egg whites). Add the cream of tartar and salt. Beat until the whites are stiff, but not dry.

Beat in the vanilla, then the brown sugar 2 tablespoons at a time. (If the brown sugar has any lumps, sift it before adding it to the egg whites.) Continue to beat the egg white mixture until it is very stiff, then fold in the walnuts.

Preheat the oven to 250°F.

Drop by heaping teaspoonfuls, onto well-greased and lightly floured baking sheets. Bakes at 250°F for 30 minutes or until pale tan in colour. Remove the cookies from the baking sheets immediately and place them on a wire rack to cool.