Jaffna House, across & along a bit from Tooting High Road tube.
This may be my favourite Tamil restaurant in the world; certainly in Tooting. It's an under-prepossessing Formica caff that's renowned as the Best Sri Lankan Restaurant.
Supposedly, there's a posher 'tandoori' dining room round the back. I've never seen it, because all the action is upfront, where old Tamil geezers in unlikely sportswear grumble to the long-suffering waitress and plump Anglo-Indian families binge on weird stuff you can't get elsewhere, like pittu and string hoppers with sothy.
The spinach, which is somehow creamy and subtly spiced in a way that mystifies me, & aubergine, which is dark and accented with tamarind, are my favourites. Sometimes - in fact, often - I just have those two curries and a stack of chapatis (two per order; I usually need four), plus a salt lassi.
On the subject of drinks, do check what's coming with the thali, because you might otherwise end up with Coke. Today, it was Sunkist orange, which I can do, but otherwise I try and exchange the free drink for a cup of tea, which is not always possible, things being what they are.