Spray a jelly roll pan (mine is 12x18 inches) with PAM or similar non-stick spray.
Sprinkle all 3 cups of rice krispies into the pan, spreading evenly.
n a regular sauce pan over medium heat, mix together 4 sticks (1 lb) butter and all the brown sugar. You will stir constantly until the temperature reaches 300 degrees. Be sure and stir the entire time!
Next, pour the toffee mixture over the rice krispies. Be sure and pour evenly over the pan. Once it is all in the pan, spread out to any areas it might not have reached. Do this delicately so things don't stick and get out of hand! Make sure the toffee is covering the rice krispies and gently push them together.
Once everything is even, sprinkle both bags of chocolate all over the toffee. You can do 2 bags of one flavor, but my family likes to mix them.
Place the pan into the preheated oven for 2-3 minutes to soften the chocolate chips
Remove from the oven and spread the melted chocolate all over the toffee.
Allow to cool for several hours. I prefer to score my toffee (usually ½ hr to 1 hr after coming out of the oven), but it is perfectly fine to break it apart.