This is in my house, not my aunt's. The paper is PAPER, not vinyl, and probably installed in the 1930s or 40s.

I would check with my wallpaper store....there used to be some "putty" like stuff that absorbed the grease. Too bad it isn't in a spot to hang a picture over.

Try some baking soda or talcum powder. Rub some into the soiled area and let it sit. Then vacuum or brush it off. You may have to repeat it several times from the looks of the spot. Hope that works, but it may not since you are dealing with paper instead of fabric.

The baking soda is a fine idea.

Steam? To melt the butter and then blot?

I'd try my steam machine --squirt, brief wait, blot; on and on.

As for the oil in the butter, maybe some Simple Green and blot, blot, blot.
Simple Green was developed to clean the oil residue in oil tankers.

OK, Checked Haley's Hints--got nothing.

Did a search and found this: (I think we have a winner here!)
On wallpaper, scrape off as much as possible, then use warm iron and absorbent paper. Treat remaining stain with paste of cornflour and a grease solvent. Allow to dry, brush off, and repeat if necessary.

My words: grease solvent could be Simple Green or LesToil (if you can find that).
Iron on LOW setting. Paper is paper towel or brown paper bag/roll. Iron; move paper; iron.....

This message has been edited. Last edited by: M-ma,