The simplest traditional method of preparing masala chai is through decoction, by actively simmering or boiling a mixture of milk and water with loose leaf tea, sweeteners, and whole spices. Indian markets all over the world sell various brands of "chai masala", (Hindi चाय मसाला [chāy masālā], "tea spice") for this purpose, though many households blend their own. The solid tea and spice residues are strained off from masala chai before serving.
The method may vary according to taste or local custom: example, some households may combine all of the ingredients together at the start, bring the mixture to a boil, then immediately strain and serve; others may leave the mixture simmering for a longer amount of time, or begin by bringing the tea leaves to a boil and only add the spices toward the end (or vice-versa).
A common Maharashtran practice for preparation of one cup of chai is to first combine one half cup of water with one half cup of milk in a pot over heat. Sugar may be added at this point or after. Ginger is then grated into the mixture followed by adding a "tea masala". Although the ingredients may vary from region to region, "tea masala" typically consists of cardamom powder, cinnamon powder, ground cloves, ginger powder, and pepper powder. The mixture is brought to a boil and 1 teaspoon of loose black tea is added. The chai is immediately taken off the heat, covered, and allowed to sit for approximately 10 minutes to allow the black tea to infuse into the chai. The chai is then strained and served.