In a heavy-bottomed pan, boil 1 liter of full-fat milk. Once it starts boiling, add 2 tablespoons of lemon juice or vinegar to curdle the milk. Stir continuously until the milk curdles completely.
Place a muslin cloth over a strainer and pour the curdled milk to separate the paneer (cheese) from the whey. Rinse the paneer under cold water to remove the sour taste of lemon juice or vinegar.
Squeeze the muslin cloth to remove excess water and hang it for 30 minutes to drain the remaining water. After that, knead the paneer for 5-7 minutes until it becomes smooth and soft.
Divide the paneer into small equal portions and shape them into small, flat balls. Set aside.
In another heavy-bottomed pan, boil 1 liter of full-fat milk and add 1/2 cup of sugar. Stir until the sugar dissolves completely.
Add 1/4 cup of coarsely ground pistachios and 1/4 teaspoon of cardamom powder to the milk. Mix well and simmer for 10-12 minutes.
Gently add the paneer balls to the milk mixture and cook for 15-20 minutes on low heat. The paneer balls will absorb the milk and become soft and spongy.
Allow the pista rasmalai to cool down and then refrigerate for at least 2 hours before serving. Garnish with chopped pistachios and saffron strands.