CHRISTOPHER: Ooh, I gotta say, this isn’t like the chai lattes in Boston.
LORELAI: Yeah, well, expecting Luke to make a chai anything was completely insane.
Chai tea is a tea beverage originating in India; in Hindi it is called Masala chai, or “mixed spice tea”. Recipes vary, but it’s based on strong black tea combined with spices such as cardamom, pepper, and ginger, with milk and sugar added. A cinnamon stick is often added for a sweet-spicy flavour. A chai latte is produced by steaming and frothing the milk before adding it to the spiced tea. The drink became popularised in the west in the 1990s.
Did Luke really not know how to make chai tea, or did he deliberately sabotage Christopher’s drink? Lorelai suggests he just put an old stick in a cup of tea, which seems like more than simple incompetence (especially as he could have said the diner didn’t provide chai lattes). Seeing Lorelai happily walking around town with Christopher while he was visiting Stars Hollow must have been deeply annoying for Luke, especially as Lorelai and Christopher had sex the last time he was there.