Mix 2 cups sugar and 1 cup cream. Cook, stirring occasionally until soft ball is formed. Add 1 cup dates. Cook to hard ball stage. Remove from heat and add 1 cup chopped black walnuts. Add 2 teaspoons vanilla. Cool at room temperature without stirring until lukewarm. Beat until stiff enough to be kneaded. Shape into long roll and wrap in waxed paper or damp cloth. Let stand until cold. Remove cloth and cut into slices.