This is how I make my sticky black rice with mango. fistbump tek, was just about to say that is my favorite!
Bring to boil 3 cups of water, a pinch of salt and 1 cup black rice in a saucepan, and then immediately cover, switch heat to low and cook for 45 mins. Some fancy rice cookers like mine do an okay job but I like stovetop better for this. Stir in 1/2 cup sugar, 1 1/2 cups coconut milk (it wont be the whole can, reserve it for later) and another pinch of salt. Bring to boil on high and then reduce that to low and cook uncovered for 30 minutes, stirring occasionally (you want it to thicken and the rice to get to your preferred level of chewiness). Remove from heat, serve warm or room temp with fresh mango sliced on top and the remaining coconut milk drizzled on top.
There are more solid preps but my family likes this softer pudding one best.