Add 1 litre or 4 cups milk in a heavy pan and bring to a boil.
Add the rice grits and saffron soaked milk.
Mix well and cook in medium flame until the rice gets completely cooked. It will take anywhere between 15-20 minutes in medium flame for the given quantity.
Add 1/2 cup sugar and mix well. Also add slivered almonds and mix well.
Simmer for 15-20 minutes for the phirni to thicken well.
Add pounded green cardamom and dried rose petals. Mix well.
Simmer for 5 more minutes and remove from flame.
Cool to room temperature, divide among serving bowls, cover and refrigerate for 3-4 hours.
Serve phirni chilled with chopped almonds, crushed rose petals.