Caramelize
Caramelizing is the slow melting of sugar, or of foods that contain natural sugars, over heat until it liquefies and turns a golden to deep amber brown. As sugar heats past its melting point it breaks down and transforms, developing a distinctive nutty, toasty, slightly bitter-sweet flavor and a rich color. The trick is doing this gradually and watching closely, because sugar goes from perfectly caramelized to burnt very quickly.
This technique gives you the topping on creme brulee, the base of caramel sauce and candies, and the deep sweetness of caramelized onions cooked slowly in a bit of fat. For plain sugar, use a heavy pan and low to medium heat, and resist stirring too much once it starts to melt, since stirring can cause it to crystallize. For onions, patience is everything: cook them low and slow for thirty to forty minutes, stirring now and then, until they collapse into a jammy, golden tangle.
This technique gives you the topping on creme brulee, the base of caramel sauce and candies, and the deep sweetness of caramelized onions cooked slowly in a bit of fat. For plain sugar, use a heavy pan and low to medium heat, and resist stirring too much once it starts to melt, since stirring can cause it to crystallize. For onions, patience is everything: cook them low and slow for thirty to forty minutes, stirring now and then, until they collapse into a jammy, golden tangle.