I don't know how to make vanilla chai from scratch. I use a powder mix from the grocery. It just has to be mixed with hot water. It tastes very good though. It's my favorite winter drink. I'm not much of a hot cocoa person but I can have vanilla chai every day.
I did have to try a few brands to find one I like though. Some brands have a spicier taste and I don't like that. The one I use has a hint of spice but the vanilla flavor is more dominant. And it's kind of creamy too. I like that it has everything including the sugar in it. I keep some at the office too because it's so easy to prepare.