It's a blue shorthaired cat, most likely a domestic shorthair without any breed ancestry. Most blue cats don't belong to any specific breed. It's certainly a pretty color, though... personally I'm very fond of this color
Maybe because a lot of blue cats seen on the internet are British Shorthairs, who tend to be thick and cobby and have big heads, although they really shouldn't have rolls of fat! But the shape of their head/face could look like fat rolls I suppose.