Mix the rice flour in little water.
Mix the nishasta in little water.
Heat a little milk and mix khoya in it to form a smooth paste. Heat the milk and add the khoya paste and stir well. Then add rice flour and cook for a few minutes. Add nishasta and cook till thick, stirring continuously. Now add the sugar and keep stirring till melted. Garnish with saffron (optional) and remove from fire.
Then add rose essence. Pour into a dish and sprinkle cardamom powder on top.
You may even sprinkle almonds and pistats crushed, if desired.
Put it for chilling.
After adding nishasta stir vigorously, because the firni will thicken immediately.