Chill the curd and water in the refrigerator. If you want to use saffron, soak it in 2 tbsps hot milk and let it rest for sometime.
Add curd to a large bowl. Whisk it well to break up lumps & make it smooth.
Sweet Lassi: If you do not have cardamom powder, then add few cardamoms to a spice jar and powder them. To make a fine powder quickly you can also add few tbsp of sugar and powder them.
Add sugar, cardamom powder and saffron to the smooth yogurt.
Whisk well. Pour water and whisk until very frothy. Taste test and add more water or sugar if needed. Transfer to serving glasses and garnish with chopped nuts.
Make Salted lassi: If you do not have cumin or jeera powder, just dry roast cumin on a low flame until aromatic. Cool and make a fine powder in a spice jar.
Add salt and cumin powder to the whisked yogurt. Whisk and pour water. Whisk again until frothy.
Make Mint Masala lassi: Pour curd, water, salt, sugar, cumin powder, chaat masala, mint leaves, lemon juice and chili to a blender.
Blend until frothy. Pour to serving glasses. Best served chilled.