Thanks to Jac at Tinned Tomatoes for a great suggestion: freshly grated Ceylon cinnamon from Cinnamon Hill on mango lassi. Lovely and refreshing on these hot days.
PS in subsequent recipe for Cinnamon Spiced Rice Pudding in Great British Chefs, total convert Jac writes:
"Now I love cinnamon, but I only recently came across fresh cinnamon sticks from Cinnamon Hill. They sell freshly harvested Ceylon and Saigon cinnamon sticks. The Ceylon comes from Sri Lanka and has a warmth that is almost citrussy and the Saigon comes from Vietnam and has some heat to it as well as sweetness. The difference in flavour between bottled ground cinnamon and freshly grated is immense."