Speaking of, [...] or Verbing, [...]

Question

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.

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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?

Answer 1

This seems like two separate questions, one about "speaking of" and the other about the "verbing".

The first one is simple: yes, you can say

Hablando de papas [patatas], me encantan.

A more interesting question could be the use of the verb "amar", as it is a strong verb in some countries (in Spain we always try to avoid it and use "gustar", "encantar", "querer" and others; the English "I love you" is "te quiero" in Spain, not "te amo"). And the term "papas" is widely used in Latin America, but in Spain sounds a bit colloquial (maybe like the English "tater"), we prefer "patatas".

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Regarding the other question, your options are just fine. Your sentences can be translated as you say. Here you have another option:

De camino a Correos, vi a Juan. [In Spain the national company handling the posting service is "Correos", so we can use that name to replace "oficina de correos".]

Answer 2

There are some expressions that are very natural in Spanish, for each of these.

A propósito de la papa... ¿has probado alguna vez la papa amarilla del norte de Europa? Es riquísima.

Al caminar a la oficina de correos, vi a John.

Here's another example of that construction:

Writing fast results in sloppy handwriting. Al escribir rápido, la letra no me sale muy clara.

Your ideas and the others on this page do work, but I wanted to make you aware of these constructions.

By the way, for the particular example of walking to the post office, there's a great phrase, camino a, which means on the way to:

Camino al correo me encontré a John.

For this phrase, you don't need to be on foot.

Answer 3

Regarding "Hablando de ...", that's exactly what we say.

Speaking of Pedro, I saw him last night at the bar.
Hablando de Pedro, lo vi anoche en el bar.

Speaking of dinner, what are you doing tomorrow night? Hablando de cenar, ¿qué haces mañana por la noche?

Or the all-time famous (not a literal translation, but the equivalent saying in Spanish):

Speak of the devil and he doth appear!
¡Hablando del rey de Roma, por la puerta asoma!

It's a very common idiom.

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Regarding [verb + ing] + independent clause, your translation and use of the tense is also right. In Spanish those are just subordinate adverbial sentences defining when the action is taking place:

Walking to the post office, I saw John.
Caminando a la oficina de correos, vi a John.

And, just like in English, you can throw a "mientras" in there if you like:

While I was walking to the post office, I saw John.
Mientras iba caminando a la oficina de correos, vi a John.
Mientras caminaba hacia la oficina de correos, vi a John.