The venue is an off-shoot from Goodman, the well-liked Mayfair steak joint. ne anlama geliyor?

Bir çeviriye bakın

The venue = the place, in this case the restaurant itself (Burger & Lobster).
off-shoot = this is a phrase meaning a smaller thing that is produced from a larger thing. The word 'shoot' can mean a new growth on a plant, and that's where this comes from.
well-liked = something that is well-liked is liked by many people.
steak joint = another way of saying 'steak restaurant' or 'steakhouse'. Sounds quite American when you call a place a 'joint'.

So, the sentence means that the restaurant is a new one from the same people who run the restaurant called Goodman. It goes on to say that Goodman is a popular steak restaurant in Mayfair.