In a small saucepan, add milk and sugar. On medium-low heat, stir until sugar is melted.
Add the black tea teabags into the saucepan. Stir occasionally. Let it steep until steam begins to rise from the milk. Do not boil the milk.
Remove the saucepan from heat. Set aside with the lid on for another 15 minutes. If you want the jelly with a lighter tea flavor, you can shorten the time.
In a small bowl, add cold water and gelatin powder. Place the bowl in a bowl of hot water and stir until the gelatin powder is dissolved. The mixture should be clear.
Prepare the container that you want to place your jelly. Remove the tea bags from the milk, and pour the milk tea through a sieve to the container.
Add the gelatin mixture into the milk tea. Stir immediately until combined.
Place in the fridge overnight. Ready to Serve.