Take a thick-bottomed pan and pour in the milk. Bring to a boil, then pour in the lemon juice and stir till the milk curdles and whey separates.
The thick white separate is known as chenna, take the pan off the stove.
Next, put the chenna in a muslin cloth, refresh under running water and squeeze till the water is totally drained.
You can also store this aside for 45-60 minutes so that the entire whey is drained out.
After the whey is drained, knead the chenna using the heel of your hand. Put in the cardamom powder and sugar into this chenna and knead again.
Take a non-stick pan, add in the chenna mixture and cook on medium heat for 8-9 minutes. Make sure to continously stir this mixture while it cooks.
Once cooked, switch off the stove and place it on a large plate to cool down.
After it has cooled, knead this mixture using your palm and shape them into small round flattened balls.
With the help of a fork you can make designs on the sandesh. Press chopped pistachios into the center of each sandesh.
Serve the sandesh instantly or refrigerate and serve chilled.