Bring the milk to a boil in a heavy-bottomed pan till it starts foaming; immediately add the lime juice and stir. It will curdle right away. You should see the milk solids separate from the whey.
Pour into a colander lined with a cheesecloth. Rinse the curdled milk with cold water to get rid of the lime juice. Allow the water to drain completely.
Gather the ends of the cheesecloth and express as much water as possible. What you now have is soft paneer.
Turn the paneer onto a rolling mat or other smooth surface. Knead the paneer well to make a smooth paste.
Roll into a ball and divide into 20 equal portions. Roll each portion into a smooth ball between your palms, making sure there are no cracks.
Bring the water to a boil in a pressure cooker; stir the sugar into the boiling water until dissolved.
Gently drop each ball into the hot syrup. Secure the lid onto the pressure cooker and bring to pressure. Reduce heat to medium-low and pressure cook for 6 minutes.
Release the pressure from the cooker while running under water; remove the lid. The rasgullas should be floating on the syrup and have expanded 2 or 3 times in size.
Pour the rasgullas and syrup into a bowl. Gently stir the cardamom and rhum agricole into the mixture. Sprinkle the pistachios over the rasgullas.
Refrigerate to chill completely before serving cold.