Failed ingredient substitution

Have you ever tried to substitute an ingredient in a recipe that made sense in your head only to fail it horribly??

Once my mom was following a recipe for korean fried chicken and recipe required mustard paste. She was not really familiar with the mustard paste taste at that time as she never tried it.

So my mom thought "Why not I blend mustard seeds with some water to make a paste and use it in recipe." She did get skeptical and used a very tiny amount but still the wings were inedibly bitter

Now looking back at it I honestly have no idea what was going on in her mind cause they are two completely different things.