Learn Portuguese (Portugal): Enquanto estamos a pensar, alimentamos a essência. - While we are thinking, we feed the essence.

Instead of using the continuous verb form, you could treat the act of thinking as a noun. You might say O pensar alimenta a essência (Thinking feeds the essence). When you substantivize an infinitive, you treat it like a masculine singular noun, usually adding the definite article o in front of it.

So does the phrase a pensar count as a substantivized infinitive here?

Technically, no. The phrase estamos a pensar is simply the standard European Portuguese present continuous tense ("we are thinking"), using estar a + infinitive. However, structurally, putting the preposition a before an infinitive treats the verb somewhat like a noun ("we are at thinking"), which is why it conceptually ties into this lesson.

I remember that conjunctions sometimes trigger the subjunctive. Why is estamos in the indicative mood here?

The conjunction enquanto (while) only requires the subjunctive mood when it refers to a future or hypothetical situation. Because this sentence states a factual, ongoing reality occurring in the present, it uses the indicative mood (estamos).

Is alimentamos only used for eating physical food?