In a large saucepan over medium heat, combine the sugar, corn syrup, water, and
salt. Heat, stirring, to boiling, then continue to cook, using a candy thermometer
to monitor the temperature.
Beat the egg whites until they are stiff and form peaks. Don't use a plastic
bowl for this. When the sugar solution comes to 270 degrees F (soft-crack stage).
Remove from the heat and pour the mixture in thin streams into the egg whites, blending
completely with a mixer set on low speed. Continue to mix until the candy begins
to harden to the consistency of dough. This may take as long as 20 minutes. Add
the semisweet chocolate chips. Remember that the candy must already be at the consistency
of dough when you add the chocolate; the nougat will thicken no more after the chocolate
is added. When the chocolate is thoroughly blended and the nougat has thickened,
press it into a greased 9-inch square pan. Refrigerate until firm, about 30 minutes.
With a sharp knife, cut the candy in half down the middle of the pan. Then cut
across into 7 segments to create a total of 14 bars. Melt the milk chocolate chips
in the microwave for 2 minutes at 50%f power, stirring halfway through the heating
time. Melt completely, but be careful not to overheat. Resting a bar on a fork (and
using your fingers if needed), dip each bar into the chocolate to coat completely
and place on wax paper.
Cool until firm at room temperature, 1 to 2 hours.