Instead of raw rice, you can use readymade Rice flour as well. You can add the flour directly or make a slurry before adding it to the boiling milk.
When the milk comes to a boil, add the rice flour and mix well.
Simmer for 5 mins, taking care to keep stirring.
Add the crushed dried rose petals and keep stirring to avoid lumps.
About 10 mins, the mixture will start to thicken.
Add the sugar and mix till it dissolves completely.
Allow to cool and pulse it a couple of times to remove lumps if any.
Add in the finely chopped nuts, transfer to serving bowls and garnish with more nuts, rose petals
Gulab Phirni is mostly served chilled.
So refrigerate before serving.