Broken manifold stud in head

Which engine? If it's a slant, no worries. Burn the mess out with a cutting torch deep enough for a 1/2" long plug. Drill and tap for the plug and put it in with Loctite until it is flush with the surface. Then drill and tap the center of the plug for the new stud. You will be into water so make sure everything gets some thread sealer. Crude, but it works.