Crush the spices lightly. Use the back of a spoon to crack the cardamom pods and break up peppercorns. This helps release flavor without turning them into powder.
Simmer the spice base. Add cinnamon sticks, cardamom, cloves, peppercorns, and sliced ginger to a saucepan with 2 cups of water.
Bring to a gentle simmer for 8–10 minutes. You want fragrant steam, not a rolling boil.
Steep the tea. Turn off the heat, add the tea bags or loose leaf in a strainer, and steep 4–6 minutes. For stronger chai, go up to 7 minutes, but avoid bitterness by not leaving it much longer.
Sweeten while warm. Remove tea bags or strain out loose tea and spices.
Stir in your sweetener to taste while the liquid is warm so it dissolves evenly. Start with 2 tablespoons; you can add more later.
Add vanilla. Stir in vanilla extract or scraped vanilla bean. This rounds out the spice and gives you that cozy café-style flavor.
Chill the concentrate. Pour into a jar and let it cool to room temperature, then refrigerate until cold.
Cold concentrate helps keep your ice from melting too fast.
Assemble the latte. Fill two tall glasses with ice. Add 1/2 to 3/4 cup chai concentrate to each glass, then top with 1/2 to 3/4 cup milk, depending on how strong you like it. Stir gently.
Taste and adjust. Add more sweetener, a splash of milk, or a dash of cinnamon if needed.
If you like a foam top, froth a bit of milk separately and spoon it over.
Serve. Garnish with a cinnamon stick or a light sprinkle of ground cinnamon. Sip and enjoy immediately.