Wash and grate the carrots. Soak the raisins in water for 30 minutes. Blanch and shred the nuts. Put the water to boil, when it starts boiling add the grated carrots. Cook for 5-7 minutes. Add the milk. Cook on a low flame for 1 hour stirring occasionally. Add sugar, mix well and cook till the sugar has dissolved and all the milk has been absorbed. Add ghee and simmer for 2-3 minutes. Add the slightly crushed cardamoms and the raisins. Mix well. Remove the gajjar halwa from heat and arrange in a serving dish. Garnish with almonds and pistachios. Serve cold, hot or at room temperature.