As Blackfriars Road is rather long, it's worth adding that it's near where Webber St crosses it.
I did notice the other week in the forum that someone was thinking of taking their parents there. I would recommend this, my parents like it as much as TAS.
It is a friendly, relaxed and relaxing place, has both a cheap bar menu (£5 a dish) and a good value restaurant menu (£8-12 a dish). The latter regularly changes and is modern european - with lots of unusual things, that I have not seen anywhere else. It is a slightly out of the way gem! As is Mar -i-tella, but that's another story ....
PS in case you were wondering it is named after a Laurel and Hardy film about a dog called "laughing gravy"
Laughing Gravy is one of a number of good and useful restaurants in SE1 - Kitchen & Bar, Tas, Konditor&Cook at the Young Vic, Meson Don Felipe.
Laughing Gravy is regarded as the house canteen for all the businesses in the starter units at Blackfriars Foundry and an excellent place to meet after work. They have a love/hate relationship with it : the smells from the kitchen penetrate several of the offices and may make you rather hungry when you just have to complete that pitch!
The menu has standards but also, as mentioned, is quite adventurous. I seem to remember antelope on the lunch menu.