In Oz, I've used a tamarind concentrate paste branded TAMICON, product
of India. Its says 1 teaspoon for a dish sized for 6 persons
(subjective hey). I usually soften it in a 1/4c hot water and add that
to the recipe.
I see it's like Tabasco sauce - the jar is dated 1998! Just about
finished now, think I'll chuck it out and splurge on a new jar LOL

Cheers
-- Bronnie