Translation:I would have stopped talking when you asked.
It reads like an incomplete sentence, "I would have stopped talking when you asked, if you hadn't pulled that face."
Question time: why is "de falar" translated here as a gerund rather than an infinitive, is it the preposition or it is the past participle before it (parado)? Also would the sentence make more sense with "se" instead of "quando" or is that me using English rules?
1- when, in English, you have "stop+gerund" in Portuguese it turns to "parar+de+infinitive" (não pare de dançar - don't stop dancing). 2- if you use "se" it would be "se você tivesse pedido".