It's much easier than you'd think. Just time consuming. But I do it two or three times a year, when those lovely little yellow-orange mangos are in season (there are a couple of breed names; I believe my fav is called "champagne"), because it's one of my absolute favorite dishes.
Glutinous Rice with Mango
Khaw Neaw Mamuang
3c glutinous rice
6 ripe mangos, well chilled
1.5c coconut cream
1.25c thick coconut cream (I've never figured out what the "thick" part means -- possibly you could use a lower-fat cream for the regular, and a higher-fat one for the thick -- but it works fine just using regular coconut cream for both *shrug*)
2T toasted sesame seeds (or chopped cashews or other nuts)
Soak the glutinous rice in ample cold water for 2 hours. (I keep it in the fridge while it's soaking.)
Line a steamer with cheesecloth (only really necessary if your steamer doesn't have an interior bowl -- like, if you're using one of those metal steamers that you put inside a regular pot), heat steamer, spread the glutinous rice on the cheesecloth, and steam for 30 minutes or until cooked through. The rice will become glossy.
Towards the end of the rice's cooking time, mix the SEASONINGS ingredients in a large bowl. Gently mix in the hot steamed rice. Cover tightly and let soak for 30 minutes to absorb the coconut flavor.
Blend the SAUCE ingredients in a saucepan and heat it just to the boiling point. Turn the heat off, pour the sauce into a container from which it can be dispensed (e.g. a measuring cup with a spout) and leave to cool.
Peel the well-chilled mangos, slice lengthwise, and remove the pits.
Divide the rice among 6 plates. Place the chilled mango slices on top and drizzle with sauce. Sprinkle with toasted sesame seeds and serve.
Adapted from Practical Thai Cooking, by Puangkram C. Schmitz and Michael J. Worman, ISBN 4-7700-2181-X, p 169.
I should note that I generally just take the ingredients for both the sauce and seasoning, mix it all together, bring the whole batch to boiling briefly, and mix that into the rice. Makes it slightly richer, and dispenses with having an extra dish around for pouring the sauce.