Flat White on Berwick St in Soho, London.

They take their coffee extremely seriously there. More than once i've ordered a coffee and listened to the baristas have heated arguments with the lingering barista friends over the best modifications to make to their expensive coffee machines to achieve optimum results.

"Ooooh! A X3 filter on a Mk. 5 steamer! Interesting!" (or whatever - all a different language to me).