This is the same method we use to test every batch before it ships, five steps, no shortcuts. Skip one and the chai still works, technically, but it won't taste like much beyond hot, milky, vaguely spiced water. Follow all five and the difference is obvious by the second sip.
Measure the ratio
One heaped teaspoon of chai per cup, to half water, half milk. Too little and the spices never bloom. Too much and it turns bitter before the milk has a chance to balance it out.
Start with water, not milk
Bring the water to a boil first and add the chai to that. The spices need real heat to release their oils. Adding milk too early mutes them before they've had the chance to open up.
Simmer, don't rush it
Let it simmer on low for 3–4 minutes once the tea's gone in. This is the step people skip most often, and a 30-second steep tastes like flavoured water, not chai.
Add the milk, then bring it back up
Pour the milk in and let the whole pot come back to a gentle boil once, not a rolling boil, just enough to fully marry the milk with the brew.
Strain well, sweeten to taste
Strain through a fine sieve, pressing the spices to get every last drop of oil out. Sweeten after straining, not before, you'll use less, and taste it more clearly.