I found most of the ingredients at Duc Loi, a Vietnamese grocery store at the corner of Mission and 18th Streets in San Francisco. They had the key ingredient - fresh curry leaves, although they can be purchased online here and here. Duc Loi also had the plain Chinese steamed buns (mantou) that the recipe calls for. I recommend not omitting these - they are so yummy when dunked in the creamy butter sauce! I can't find an online source, but if you can't find them at your local Asian market (or don't have a local Asian market) here is a recipe for mantou. The bird's eye chilies can be found at Asian markets or online.
The recipe is really easy to make, and doesn't have too many ingredients or too many cooking steps. I hope I've made the shopping easier by providing online sources. This is so worth making; the creamy sauce has the unique curry leaf seasoning, and isn't too spicy, and combined with the succulent crab and the crunchy, sweet mantou - oh! So good!
Get the recipe! Rasa Malaysia's Creamy Butter Crab
(Image: Kathryn Hill)