I have noticed after the engine warms up after roughly 10 mins of driving that from around where the steering oil is or just behind / underneath some white smoke is coming. It does not smell lethal but it is not pleasant when you can smell it in the cabin when driving.

It has left a white deposit on the inside of the bonnet lid and around where the smoke has emmerged from. The engine is extremley clean and I would like to keep it that way; any suggestions what this could be.

It is a small problem that doesn't effect the driving but if it is a leak somewhere (that it seems) is it common. I would like to nip it in the bud before it gets worse.

Help... Please advise

could be the steering tank(leak somewhere),or from some connection which is coming out of the tank.It also has like a nut on the edge check that is not loose or something..

Could be your rocker cover gaskets shot and leaking oil onto the exhaust which burns it once hot.

I had this and left it until one day I had to pull over as I thought the car was on fire, loads of smoke coming out through the scoop. Fortunately it wasn't but it was time to get the gasket changed!

The power steering fluid tank is sealed by an O - Ring which has a bad reputation of leaking its just a simple matter of removing the small bolts holding the tank in place and lifting it straight up and you will see the O Ring in question. I had leaking problems with mine and after getting a new one from Subaru themselves it still leaked!!! I tried replacing it and the second one seemed to be a bit better, Its been about 3 months since I did it and now it has totally sealed so I suspect you need to replace this O Ring under the tank. Good Luck