1Using a pastry blender or fork, combine the butter, flour and brown sugar until the mixture forms fine crumbs. Press the mixture into an ungreased 9x13 inch pan. Sprinkle the crust with the pecan pieces. Set aside.
Combine the butter and the brown sugar in a sauce pan and bring to a boil over medium heat. Stir constantly.
Allow the mixture to boil for 1 minute. Drizzle the mixture evenly over the crust. Bake the crust for 20 minutes at 350 degrees.
Immediately after removing the crust from the oven, sprinkle it with chocolate chips. Allow the chocolate chips to stand for 5 minutes so that they melt, then spread evenly over surface of the bars.
Let the bars cool, then cut into desired serving size.