This simple recipe was first published in Madhur Jaffrey‘s Indian Cooking. I believe the basic principles are broadly agreed upon but the enthusiastic chai-wallah community will offer you many variants! One common addition generally agreed upon to add warmth is a slice of fresh bruised ginger.
1-1/2 cups water
1 inch stick of cinnamon
8 cardomom pods
8 whole cloves
2/3 cup milk
6 tsp. sugar (or to taste)
3 teaspoons any unperfumed loose black tea
Put 1-1/2 cups water in saucepan. Add the cinnamon, cardomom, and cloves and bring to a boil. Cover, turn heat to low and simmer for 10 minutes. Add the milk and sugar and bring to a simmer again. Throw in the tea leaves, cover, and turn ff the heat. After 2 minutes, strain the tea into two cups and serve immediately.