In top of double boiler, melt chocolate until smooth. Stir in condensed milk and cook for 5 minutes, or until slightly thickened. Remove from heat and stir in 1/4 cup of the nuts. Let cool 30 minutes, or until thick enough to hold its shape.
Scrape the mixture onto a piece of waxed paper to form the mixture into a log. Roll the log in the remaining 1/4 cup of pecans. Wrap and chill until set.