Rinse 1 cup glutinous rice
In a pot, combine 6 cups water and the rice
Bring to a boil over medium heat
Stir occasionally until the rice starts to soften
Add 1/2 cup cocoa powder
Add 1/2 to 3/4 cup sugar, to taste
Stir until the cocoa and sugar are fully dissolved
Simmer until thick and creamy, stirring often
Add more water if needed to adjust consistency
Serve hot
Top with evaporated milk if desired