Sounds like you're talking about the FPGA evolution experiments Adrian Thompson and others did in the 1990s: https://evolvablehardware.org/history.html

Indeed! With the keyword "evolving circuitry" I was able to find the blog post [1], with only one submission 8 years ago that barely got traction [2].

Thanks!

[1] https://www.damninteresting.com/on-the-origin-of-circuits/

[2] https://news.ycombinator.com/item?id=18099226