I don't understand why there is an «à» between soirée and parler? I there a connection with passer as in passer à translates to the original text?

Hi G.W.,

You are correct in mentioning the verb passer as when you spend time doing something in French it will be -

passer du temps à faire quelque chose

Hence, "passer la soirée" will take the preposition à and by extension other indicators of time as in the following examples :

Hope this helps!