First, make chenna. Follow this post to see details of how to make chenna
After the chenna has drained of extra moisture for about 30 minutes, give it a whizz in a blender or mixer to make it smooth and let out more water.
Remove and knead well for 3 minutes. At the end of it, you should be able to make smooth balls out of the chenna easily. If not, knead for a bit longer. The size of the rasgulla will double on cooking in sugar syrup so remember to makem smaller to begin with
Add the sugar and water to your pressure cooker and bring to boil. Mix well for the sugar to dissolve, lower heat to very low and add the rasgulla balls gently into the syrup.
Cover the pressure cooker and cook without whistle for about 7-8 minutes on medium-low flame.
Turn off heat and wait 5 minutes before opening the cooker lid. You'll find spongy rasgulla that's doubled in size!
Cool completely, add crushed pistachios on top and refrigerate rasgulla in syrup until ready to serve