Measure 150 ml of the milk-brewed tea. Add to a pan with sugar and skim milk. Mix and turn on the heat.
Use a spatula to stir it once it starts to thicken. It should be done in about 10 minutes from the time you turn the heat on. It will thicken as it cools, so there's no need to reduce it (please don't!).
Turn off the heat and stir until it's silky smooth.
Check out this related recipe for condensed milk. Recipe ID: 617420.
Story Behind this Recipe
To create this, I reworked my recipe for condensed milk.
The key to making this is turning off the heat when you're wondering if it's thickening or not. If you turn off the heat prematurely and it's watery, heat again. It hardens when chilled. If it becomes too hard, reheat it.