Place the evaporated milk and the condensed milk in your heaviest pot. Add the cinnamon sticks and a pinch of salt. (Salt is not traditional but helps intensify the flavor).
Cook over medium low heat, stirring constantly. The water will begin to evaporate as steam.
Stir steadily with a wooden spoon or heat-proof spatula so that the mixture does not stick to the bottom of the pan and burn.
Adjust the temperature so that the mixture stays just barely at a simmer.
