Combine water, cardamom powder, and jaggery in a bowl and bring it to a boil. Cook the jaggery syrup over medium-low heat, constantly stirring until the mixture boils.
Once the jaggery syrup reaches the hardball stage (at 265° F), the color of the syrup will become darker, like dark amber color.
Check the consistency - the gur syrup will look thick (almost like 2 string consistency), and when dipped in syrup, it will coat the back of your spoon. That shows your syrup is ready.
Another alternative way to check the consistency is to spoon a drop of the jaggery syrup into the cold water.
If it sinks to the bottom and solidifies immediately, you can be assured that you are on the right path and march forward. On the other hand, if it dissolves, it needs to be boiled further.
When removed from the water, the jaggery will harden to a brittle consistency, and if pressed, it will snap. Take the syrup off the flame.
Add the roasted peanuts and mix until all the peanuts are coated well with the syrup.
Work very quickly here, as the mixture will harden pretty fast.
Spread the peanut mixture to a greased flat plate and cover it with parchment paper.
Roll the peanut chikki mixture to 1/4-inch thickness using a rolling pin. Lift the parchment paper and mark the chikkis with a sharp knife into squares.
This way, the gajak will snap easily once cooled. Set it aside to cool completely.
Cut and store the pieces in an airtight container. Good for 3-4 weeks.