Bake the waffles to the desired degree of caramelization - as darker, as the more caramelized they will be. By the way, if the waffles are cold, you can always reheat them in a toaster. Pearl sugar, which is commonly used for Liège waffles, is heat resistant. It gives them a crispy texture and a light caramel flavor. Well, if you can't find it, don't worry, the waffles will still be delicious. Another recipe in your piggy bank, how to use excess sourdough.