A dead-ripe fresh mango is more delicious than any frozen fruit. But if you can't find one, use frozen mango, which will make a thicker, slushier shake. If your mango isn't ripe, just add a squeeze of honey to the lassi.
To make, combine ¾ cup mango chunks (frozen or fresh and very ripe), ½ cup Greek yogurt, ¼-⅛ tsp. ancho chile powder, scant ⅛ tsp. salt (optional), and ¼ cup water in a blender; purée until smooth.