"Always buy spices regularly in small quantities to maintain their freshness". And she also grinds her own spice powders, sometimes using her mortar and pestle, but usually an electric spice grinder.
"Like crepes, the first few dosas may turn out a bit ragged. Dosas can be tricky, but with practice, anyone can master them."
Dried red chiles are available in Asian and South Asian grocery stores and in large supermarkets. Grind them to a powder in a spice grinder, or buy them already ground, and usually labeled "dried red Indian chilli power".
Cayenne pepper is a substitute and easy to find, but often has more chile heat, so be cautious.
Urad dal is small legume, pale gray with black skin, and is usually sold split and skinned. It is widely available in South Asian stores, as are mung dal, toovar dal and masur dal.
Tamarind pulp and curry leaves (fresh or frozen) can also be found in Indian or South Asian grocery stores.
Canned coconut milk is a perfectly acceptable substitute for fresh coconut milk, and often used in Indian kitchens.