In a mortar and pestle, crush the knob of ginger into chunks to release the juices and expose more surface area. Add the cinnamon sticks, star anise, cloves, roses, cardamom pods, and black peppercorns into the mortar and use the pestle to lightly crush them so they release their oils. Lastly, use a microplane to grate a bit of nutmeg.

Transfer all of the spices from the mortar to a medium sized pot. On medium heat, dry roast the spices for a minute, or until they're fragrant. Use a wooden spoon to stir them around every 10 seconds so they don't burn.

Pour the water in with the spices and bring it to a light rolling boil for 3-5 minutes, or until fragrant.

At this point, add in the black tea leaves and mix really well. Simmer the spices with the black tea for 5 minutes. Be careful not to boil it for too long, otherwise it will be very bitter.

Remove the pot from heat and pour in the sugar. Stir until the sugar has fully dissolved.

Allow the spices and tea to steep in the hot water for at least 15 minutes. Then, strain the chai concentrate into a sanitized pitcher with a lid. Store in the fridge for up to five days.

Use a 1:1 ratio of concentrate to milk. The concentrate can be served steamed, heated, or chilled.