Heat the water in the saucepan. While you wait, crush the spices (except the pre-grated ginger) using your mortar and pestle or spice grinder. They don't have to be powdered, just crushed to release their flavors.
2 cups water
Add all the crushed spices and sugar to the water. Boil on medium for three minutes and add the tea baggies, then let boil for two more minutes.
2-3 tsp loose black tea, 2 green cardamom pods, 1 inch ginger, 2 cloves, 1/2 cinnamon stick, 5 black peppercorns, 2 tsp sugar
Add milk and vanilla extract (optional) to the saucepan. Let the contents come up to a boil again, then turn off the heat. Cover with a lid and let sit for 2-3 minutes.
1 cup whole milk, 1 tsp vanilla extract
Strain the masala chai into the mugs. Add the rum and top with whipped cream. Optionally, sprinkle some cinnamon on top.
Notes
Use the spices you like. I included basic masala chai spices here, but there are more options: allspice, star anise, fennel seeds, nutmeg...
If you're not into rum, you can also prepare this spiked chai drink with bourbon or whiskey.
There are different types of black tea. Try a bunch to see which is your favorite!
If you prefer, use frothed milk instead of whipped cream.