Steps
1. Wash rice and soak in one cup water for 30 minutes, then drain in a strainer for one hour. Put some grains, a little at a time, on a chopping board and crush into small pieces by pressing them lightly with a rolling pin.
2. In a heavy pot, bring to a boil 4 cups milk; reduce heat to medium and continue boiling, stirring from time to time until milk is reduced to 2 cups.
3. In another pot, boil 4 cups milk.When it starts boiling, add rice. (It is good to wash rice before adding it to milk). Cook over medium heat, stirring occasionally until rice is done. Add 2 cups thick milk, sugar, and raisins,stirring constantly.
4. When the mixture starts boiling, remove from heat, and add rose water. Pour firni in a dessert bowl. Garnish with almond and pistachio slices.

Source
International Rice Institute (IRRI) & International Women's Organization (SUHAY), VIRMANI, Inderjeet (ED)(1991), Home Chefs of the World - Rice and Rice-based Recipes, ISBN 971-22-0023-X, Manila, Philippines