We used a proprietary syrup when I worked there about a year ago, but I know there were rolling out a new type of concentrate. Don’t know if it was still our own recipe or if it’s what surlygirl suggested. The formula was 3, 4, and 5 “pumps” for 12, 16, and 20oz cups respectively. Not sure how much liquid is in a pump, but it’s definitely not a 1:1 ratio. Add the syrup to the cup, steam/froth the milk, pour so that it hits the back of the cup, mixing the syrup without having to stir. Milk was heated to about 160 degrees, and personally, I recommend using vanilla soymilk. I think it complements the flavor of the chai better.