In a heavy saucepan, melt the sugars with the corn syrup.

Using a candy thermometer, bring the temperature up to 285 degrees.

When it reaches temperature, remove from the heat and gently stir in sifted baking soda. It's important to sift it first to remove all the lumps and bumps. Don't stir too hard, you'll pop the bubbles. You want it to bubble up!

Pour it into a lightly oiled 9X13 pan and let it cool until it's hard to the touch.

Using a glass dish, melt the chocolate chips in the microwave on high, taking it out every 30 seconds to stir with a rubber spatula. Be careful not to get any moisture in it. If any moisture at all gets in, the chocolate will seize and not spread smoothly.

Once it's melted, spread it out on top and down the sides of the cooled toffee.

Allow it all to cool completely.

Once it's all solidified, break it into pieces and store in an airtight container in a dry place.