I would recommend Kroil.Correct
Hope they broke before the block and not inside.
The trick here is to spray the bolts w Liquid Wrench for a couple days before they get loosened. Makes it way easier.
Kroil makes Liquid Wrench seem like cool Kool Aid.
If they are broken off flush in the head, drilling them with a left handed drill bit before you bang in an Easy-Out might help.