Keep the milk to boil in a heavy bottomed pan, and then let it simmer for 5 minutes or so.
Meanwhile place the dates and cashews in a glass bowl with 1/2 cup water and microwave on high for 4-5 minutes till the dates are tender. Once cooled, grind this to a fine (or coarse, if you like) paste.
Add the cornstarch slurry to the milk and bring it to a boil. Then add the date-cashew paste, sugar and saffron. Let the mix simmer for 3-5 minutes and the payasam is ready.
I don't usually add cornstarch to desserts, but I wasn't sure if the date paste would curdle the milk, while bringing it to a boil, hence the precaution.
Garnish with the cashews and raisins toasted in ghee.
This tastes good both warm and cold.