Pattern?

Yesterday morning I was reading my own Checkmates and Tactics (2019), a self-published book created as a camp workbook for a youth chess camp. This book consists of exercises I have been using with developing players for nearly 15 years, as well as a glossary of tactical ideas and checkmate patterns.

Although I wrote the book, I still need to calculate when I encounter some of the exercises. Such was the case yesterday morning, although the first move was instantly obvious in exercise 76 from Saalbach,A.--Anderssen,A., Leipzig 1858.

Black to move

Nonetheless, the correct way forward was not immediately obvious when the motif reappeared during a blitz game last night.

Black to move