I started out wondering if there was any Spanish analogy to the English construction
Speaking of, [independent clause] as in
Speaking of potatoes, I love them.
The most obvious possibility is
Hablando de las papas, las amo.
but to my (untrained) ear this sounds weird.
Then I realized that in English, the construction
Verbing, [independent clause] is more widespread. For example,
Walking to the post office, I saw John.
In Spanish could this be
Caminando a la oficina de correos, vi a John.
or would you have to say something like
Mientras estaba caminando a la oficina de correos, vi a John.
? More importantly, is this natural? Do people actually talk like this?