Begin by heating a medium-sized saucepan over high heat. Combine water, a cinnamon stick, cloves, cardamom pods, black peppercorns, fennel seeds, and ginger in the saucepan. Bring this mixture to a boil, then introduce the tea bags or leaves.
Lower the heat to medium-low and let it gently simmer for 10 minutes. The color will deepen to a rich burgundy shade, and the volume will slightly reduce.
Add milk and sugar, stirring well. Increase the heat to high. Then, reduce the heat to medium and continue simmering for about 5 minutes.
Strain the chai into cups and adjust the sweetness to your liking by adding more sweetener if desired.