[Thank Satan she doesn't insist on informality. Sebastian could weep with relief (okay, no, that's an exaggeration. but only a slight one).]
The young master and I are both honoured by your kind words. [He puts down the tea pot, and turns to give her a light but formal bow.] The young master is used to entrepreneurship from home; having something similar here is, I believe, something he enjoys.
[As much as Ciel enjoys anything in life, the grumpycat. If Sebastian says nothing about his own enjoyment, well... a servant's well-being isn't that important in the grand scheme of things. Not that it isn't easy to assume he thrives when busy.]