Place butter and brown sugar in a medium saucepan and bring to a boil. Stir in 2 cups of the nuts reserving 1/2 cup for topping.
Pour into prepared pan and bake 15 minutes.
Sprinkle with the chocolate chips and let melt. Spread melted chips over the surface of the baked mixture. Sprinkle with the remaining nuts. Let cool and break into bite sized pieces. Store in airtight container in a cool place.