Pour cold water in a bowl. Sprinkle with gelatin powder. Stir until gelatin dissolves. Set aside. When the mixture starts to thicken, add boiling water. Stir to combine. Add rose water and a few drops of red food coloring to get pink color. Pour into serving glasses. Refrigerate 2-4 hours or until set.
Mahalabia:
Place milk, cream, sugar and cornflour in a saucepan over medium heat. Whisk to combine. Keep stirring. Add rose water. Cook, stirring constantly, for about 10 minutes or until it reaches thick consistency. Pour over the set jelly. Refrigerate for 2-4 hours or until set.
Garnish with chopped pistachios or almonds or rose petals. Serve chilled.