In the days when MIL was compos mentis we often used to visit on Sundays, have lunch, come home again, and then in the evening I would cook a light meal. Sometimes this was macaroni cheese.
About, say, twenty years ago I did this - except one day I mistakenly used icing sugar instead of cornflour to thicken the cheese sauce. It was completely inedible, of course, and since then I've been very careful about which one I use. (I should say at this point that I buy them both loose and they live in very similar looking jars.)
Tonight I managed a similar feat.
A standard last minute dessert - only the OH usually has dessert - is a meringue nest with fruit (in this case raspberries out of the freezer) and cream.
I tasted the raspberries which were a bit tart, so I added some icing sugar and served it up.
So what was wrong?
Clearly after x o'clock at night I cannot tell the difference between a jar containing icing sugar and one containing salt.
I am currently not that popular.