I would have done is a poor man's decoction and drained off the amount of boiling water you would need to hit your mash temp and boil that amount of runoff, after vortlauf-ing or straining somehow of course.
You just convinced me to get a propane spare. I can't imagine this happening to me.
Primary: House Rye Blonde
Secondary: Belgian Tripel (zin oak cubes), Raspberry Mead
Aging: Imperial Berliner
Kegged: Belgian Tripel