Grease a large cookie sheet; set aside.
In a heavy medium saucepan, combine brown sugar, milk and corn syrup.
Bring to a boil over medium heat, stirring constantly.
Boil and stir 2 minutes.
Remove from heat.
Add chocolate pieces, coffee and vanilla, stirring until chocolate melts.
With a wooden spoon, beat until thick and smooth.
Stir in pecans.
Spoon onto prepared cookie sheet in 2 equal parts.
Shape each half into a 10-inch-long log.
Wrap each log in wax paper.
Refrigerate about 2 hours or until firm.
Cut each log into 20 pieces.