I had 2 broken head bolts (they should be called timing chain cover bolts) on my early 05/05 build E90 N52. The outside one was easy. I just loosened the manifold bolts and pulled the front of the intake back a couple of inches. The PCV hoses and other things can stay connected which makes it much easier. The bolt shaft then spun out with a pick.
Keep in mind that interior bolts breaking is rare but if you are due for a VC gasket then go ahead and inspect. The bolt head was still sitting on the top of the bolt but it just spun when I touched it. I stuffed rags into the timing chain area to keep it from falling into the lower part of the motor. I was then able to remove the head with medical clamps. To replace the interior bolts the timing chain sprockets need to come off. That requires special tools to hold down the cam shafts.
N52 broken timing chain cover bolt under chain guide - Bimmerfest - BMW Forums