Razor blade for the win. I just mix a paste of glass stove top cleaner or such and let it sit on there for a few minutes to loosen whatever it is on it. I then take a single edged razor blade and gently scrap the crap away. I just go slowly so as not to damage the glass surface but in 4 years our stove top still looks brand new.
Turn the burner on as high as it will go and leave it on until the oven mess stops smoking. Then all that should be left is carbon and the foil should come right off. Open a window for the smoke.