I told my partner a recipe came from my grandmother. My ex taught it to me

My partner wants to put the recipe in a little collection for our friends. Under the heading, they've written 'From your grandmother's kitchen.'

It came from my ex's kitchen. Years ago, on an early date, my current partner asked where I'd learned to make it. I panicked at the idea of introducing an ex into a pleasant evening and said my grandmother. Since then I've repeated that origin a couple of times. My grandmother is alive; she just has nothing to do with this dish.

There is no ongoing contact with my ex. The recipe stayed because I like eating it. But the invented family story has made it into something my partner thinks they're helping preserve.

How do I correct this before the collection is printed? I don't want to imply I've kept cooking it as a secret romantic tribute, but I also know 'it's only a recipe' won't explain why I kept changing its history.