In a medium bowl, mix together graham cracker crumbs, 1/4 cup brown sugar, and 1/3 cup melted butter. Press into the bottom of an ungreased 9x13 inch pan.
Bake for 8 to 10 minutes in preheated oven. In a saucepan, combine 1/2 cup butter and 1/2 cup brown sugar. Cook over moderate heat, stirring constantly, until mixture comes to a boil; boil for 1 minute. Pour immediately over baked cookie base.
Bake for 10 more minutes. Remove from oven, and sprinkle with chocolate chips. Let stand for 2 to 3 minutes, until chips are shiny and soft. Spread the softened chocolate evenly over the top. Sprinkle with chopped nuts. Cool before cutting into bars.