Line bottom and sides of a 9" round cake pan with aluminum foil. Butter foil.
Mix nuts, butter, sugar, and corn syrup in a medium size saucepan. Cook over low heat until sugar dissolves. Increase heat. Cook and stir the syrup to the softcrack stage (280°).
Pour into prepared pan. Sprinkle with chocolate. As chocolate melts, spread evenly over brittle.
Cool 15 minutes. Remove candy from pan and peel off foil. When completely cooled, break into bite size pieces