Crush one 2" piece ginger, scrubbed, one 3" cinnamon stick, and 10 green cardamom pods with mortar and pestle. Transfer to a medium saucepan and add 4 black tea bags (such as Tetley British Blend or PG Tips), ¼ cup honey, 2 Tbsp. unsweetened cocoa powder, 2 tsp. vanilla extract, ¼ tsp. kosher salt, and 4 cups water. Place saucepan over medium heat and bring liquid to a boil, stirring occasionally. Pour in 1½ cups whole milk, stir to combine, and return to a boil.
Immediately strain chai through a fine-mesh sieve into mugs; discard spices and tea bags.
