In a small saucepan over medium heat, combine your water, non-dairy milk, the cinnamon stick, cardamom pods, cloves, and ground nutmeg. Bring to a boil.
Once your liquid is boiling, turn the heat to medium-low, and add your sahlab (or cornstarch slurry) and stir until thickened (2-3 minutes) using a small whisk.
Once the liquid thickens enough to coat the back of a spoon, remove from the heat, add your rose water, and strain through a fine mesh sieve. Pour into small glasses or mugs.
Garnish with more nutmeg, ground cinnamon, dried rose petals, or finely chopped pistachios (or all of the above!) and enjoy.