You can. You can use any type of chocolate chips, from semi-sweet chocolate chips to dark chocolate chips, for this delicious dish. Just know that if you use a variety or change the recipe, it will change the flavor of the chocolate syrup as well.  Using a bittersweet chocolate will cut down on some of the sweetness and richness, but some people might actually prefer that better. The best way to find the flavor that you like the best and to know the main difference between the choices is to make a few batches and try the options.