I (38M) have always enjoyed cooking and baking. My wife (37F) on the other hand, does not. So I do probably 95% of the cooking in our house and I like to think I'm pretty good at it.
My MIL (70F) is also an exceptional cook and we've both shared recipes with each other over the years. But there is one recipe that she refuses to share with me, her apple pie.
She says it's her great-grandmother's recipe and has been in the family for over 100 years. It's amazing, literally the perfect pie. After years of her making it and refusing to share the recipe I stopped asking.
But I started experimenting on my own trying to reverse engineer it and recreate it. I did this by taking a slice home every chance I could so that I could use it as a taste test.
It took a lot of test runs and failures, but this year is the closest I have ever gotten to recreating it. It's not 100% there yet, but it is damn close. I know I'm still missing something, but I haven't figured out that final piece yet.