Special equipment: a steamer or steamer baskets, cheesecloth or paper towel, food processor and Pittu steamer, see Cook's Note**
Line a steamer with several layers of cheesecloth and fill with the all purpose flour. Steam for 45 minutes. Spread the steamed flour on a baking sheet to cool.
Combine the steamed flour, roasted urad dal flour, and salt in a large bowl. Add the hot water, a little at a time, stirring with a wooden spoon, until the dough resembles cornmeal (may not need all the water). Place the mixture in a food processor and pulse until it resembles couscous.
Pour into a large bowl and mix in the crab meat, 1/2 cup grated coconut, shallots and basil. Pack the Pittu steamer** with 1 tablespoon of coconut then 1/2 cup Pittu mix, repeat until the steamer is full. Steam for 5 to 7 minutes, until the steam comes out the top of the steamer. Push the Pittu out of the steamer onto a platter.
* Urad dal flour is ground split white gram beans. It can be found in Indian stores. ** Pittu steamers can be found in specialty Sri Lankan stores.