My teacher, Mrs. Vilavong Saysavahn, told me "Get last year's rice." That's so it would be dry, and absorb the coconut milk better. I think any rice from Thailand is probably been in transit long enough to qualify. Do not use Japanese mochi - it won't work in this recipe.
1 lb. raw kao neow (sticky, or sweet, rice)
1/2 cup white sugar
1/2 cup dark brown sugar
1/2 cup thick cocnut milk
2 tsp white sesame seeds (optional)
Soak the rice in warm water for 2 hours. Drain and steam as directed in my Laab Kai recipe, but prolong the steaming until each grain can be squeezed to a paste between the fingers. Let it cool on a bamboo mat or in the bamboo steamer top.
Place the white sugar in a heavy, deep saucepan with a relatively small bottom area. Stir constantly over medium heat until the sugar liquefies (it will go through a crumbly stage first). Turn the heat as low as possible and continue to stir until the syrup is a rich brown, then remove from the heat at once.
Warm the coconut milk, then return the syrup to the heat and add the coconut milk. Stir until well combined and all the syrup is dissolved, then add the brown sugar and stir until that is also dissolved. Add the cooled rice a handful at a time, mixing and stirring over low heat until all the liquid has been absorbed and the rice forms a very sticky mass. Remove the pan from the heat.
Lightly oil a 9" pie plate and turn the rice mixture into it. Press the rice flat in the plate, smoothing the top with the back of a spoon. If you wish to add sesame seeds, toast them lightly in a heavy skillet until golden, then remove at once to a bowl. When they're cool, sprinkle them evenly onto the Kao Neow Dang.
Let the dessert cool thoroughly for several hours, then cut in squares with a warm knife, and serve.
Leftover Kao Neow Dang is delicious if left to dry for several days (separate the pieces for faster drying - do not refrigerate), then deep-fried until the outside is crispy. If you think you might do this, leave off the sesame seeds, as they tend to burn.