Combine cornstarch, sugar, and 9 cups of water in a large saucepan over medium-high heat, stirring often with a wooden spoon for 10 minutes or until the cornstarch is completely dissolved.

Bring to a boil. Reduce heat to low and simmer for 1 hour, stirring occasionally.

Add pistachios, almonds, and rose water to the saucepan. Stir until well-blended.

Pour the pudding into a 2-quart non-stick mold or a large glass serving bowl.  

Let the pudding cool thoroughly. Refrigerate uncovered. Remove from mold and serve.