Having felt him coming all the way down the street (well, who wouldn't, when he isn't deliberately masking his presence?), Xel has one of the competent waitstaff ready to meet Gaav at the door, and when said door opens, he looks up with a quick, bright wave and a smile before going back to what he's doing.
When he's finished with it, he steps back into the kitchen, and then farther, into the fridge, and comes out with a glass of red, red liquid, which he instructs that same waiter to send Gaav with the house's compliments.
Xel doesn't usually have anything to do with the wet stuff here (which is odd to him, after serving Zelas so long), but the preparation of bloodwine* is a secret. And, possibly, if Gaav stays in a good mood, the pub will be in one piece when he leaves.
* involves very unusual mulling spices. Which are also secret.