You will need:
a coffee grinder
a teapot full of black tea
sweetened condensed milk, fat-free or full-fat, as you prefer
and your favorite chai spice mixture.
What you do is whiz the spices in the coffee grinder until they are a fine power, and store them in an air tight container. You take a tablespoon or so of spices, open a small can (or tin, if you speak British) of condensed milk, and mix (a) into (b), and then stick the can into the fridge with a bit of saran wrap over the top.
When you need chai, make strong black tea--quite strong, I've been using half again as much tea as I normally do--and put a big spoonful of the milk/spice glop into the cup. Stir.
Instant chai. With no scrubbing the milk film off the saucepan after.
It makes me happy.