In a medium bowl, add Fruity PEBBLES™ and pour in the milk. Allow sitting for an hour.
In a small bowl, sprinkle the gelatin over the water and let stand for about 5 minutes.
Strain the Fruity PEBBLES™ out and transfer only the liquid into a saucepan.
Add heavy cream, sugar into the saucepan. Bring the mixture just to a simmer over moderate heat, stirring.
Remove from heat, add the gelatin and vanilla extract. Stir until dissolved.
Pour the liquid into 4 small glasses or 6 small ramekins. Let them cool down at room temperature then transfer to a fridge, covered for at least 4 hours.
Serve with additional Fruity PEBBLES™ as a topping.