Why did my chocolate tart sink in the middle?

[msrisotto]

I love it and won't stop making it just because it sinks, but what can I do to stop that happening? There's no raising agent in it. Just eggs and flour. Does it mean the oven is too hot? www.bbcgoodfood.com/recipes/1759646/brownie-fudge-pie

Make sure you preheat at the gas mark you are using so it isn't too hot and maybe try cooking it a smidge lower and longer. It might just be the nature of it because brownies tend to be dense and gooey.

Yeah, I don't really know why it rose so much in the middle in the first place.. The oven was pre heated.