Brew the tea before adding milk
Let the tea finish brewing before milk enters a mug with leaves or a bag. Then adjust the milk to the cup rather than hiding an uncertain brew.
Milk belongs after extraction in the mug
Adding cold milk to a mug while its tea bag is still steeping changes the temperature and the brewing conditions. If you want a repeatable cup, make the tea in water first, following the packet's directions, then remove the bag or basket. Now add the milk. This gives you a clear distinction between preparing the tea and deciding how creamy you want the finished drink to be.
When tea has already been brewed and strained in a separate pot, putting milk into the serving cup first is a different situation. The extraction is already finished. You can choose the order that suits you without confusing it with adding milk to leaves that are still brewing. Neither order should be used to justify pouring hot liquid into damaged or unsuitable crockery.
Choose enough flavour to remain present
A robust black tea often keeps its character after a small addition of milk. A very delicate tea may become difficult to recognise. That is a preference question rather than a prohibition. Taste a little of the plain finished tea, then add a modest amount of milk and try again. If the cup becomes mostly milk-flavoured, use less milk next time before assuming the tea needs a much longer steep.
If you want a stronger base, adjust the leaf-to-water ratio deliberately. Leaving a small portion to steep for a very long time can create a dry or harsh finish without the fullness you wanted. Keep track of the water volume, since a large mug with the same single bag may start weaker than the recipe on the packet. The amount of milk should not have to compensate for an accidental mismatch.
Keep additions fresh and personal
Use milk or a suitable plant-based alternative stored and handled according to its label. Different products contribute their own sweetness, texture and flavour, so changing the milk can change the result even when the tea is identical. Offer it separately when serving others. There is no need to make every cup the same colour. Once you find the balance you enjoy, note both the tea recipe and the approximate addition, rather than recording only how long the bag stayed in the water.
