I like a thinner, drinkable lassi as opposed to a milkshake-thick drink. Also, I prefer to have the mango flavor shine, so I don't add milk, instead thinning with a little bit of water.
I highly recommend using Ataulfo mangoes as opposed to the larger green, red and yellow 'Tommy Atkins' (they're currently the top two mangoes sold in the US). First, the flavor of Ataulfos are much more intense with a sweet-tart contrast. In addition, Ataulfo mangoes are like buttah, creamy, smooth and fiberless which means they are perfect for lassis! The small, thin pit also means more flesh and an easier time removing it.
Put into blender and blend until smooth:
1 cup plain yogurt
1/2 cup water
1 mounded cup of ice
2 Ataulfo mangoes peeled, pitted, sliced (about 2 cups or 300g)
2 tbsp sugar
squeeze of lemon juice
Pour into glasses and sprinkle on top of each drink:
dash of ground cardamom
The lassi can be made ahead and stored in refrigerator for 24 hours.