I have had this dish twice, both at Thai restaurants. The first was when I met a good friend for lunch and she suggested dessert. "You've never had Mango Sticky Rice?? We have to get it! It's amazing!" This dessert looks modest on a plate, but the attraction is in the contrasting textures. The second taste was when my husband and I went to a local Thai restaurant, and I played the opposite role this time. "You've never had Mango Sticky Rice??" And so the folklore continues like so, educating palettes one person at a time.
At Asian supermarkets, you can find small cans of coconut milk. This is convenient b/c most dishes don't require a full can.
Cook Rice in water over medium high heat. As the amount of water decreases, add coconut milk, a little at a time. Add sugar and cook until grain is cooked all the way through.
My dining companion said "It's as if one day, back in the day, someone dined at a Thai restaurant and asked for dessert and the staff was perplexed by this request....about this dessert concept so prominent in Western culture. 'What shall we do? We have a mango and we have rice. Let's figure something out!'"
Sounds like a sticky situation.