Could you please help me with this one?
I encountered this sentence "Io mi sono fatto una bistecca". I would like to ask why is here "fare" behaving like an intransitive verb?
Thanks!
This is not an intransitive verb. This is a form of reflexive voice. Italian verbs can be conjugated in three voices: active, passive and reflexive.
You can recognize the reflexive voice from the auxiliary essere and the presence of the clitic reflective pronoun (mi for the first person singular).
The reflexive voice comes in a number of flavours (for more details see the link above), but this is a case of indirect reflexive. You can distinguish it from other flavours of reflexive (like the direct reflexive, or the reciprocal reflexive) by the presence of the direct object ("una bistecca"). From the book Italiano by Serianni, XI.21-22 (my translation)
Indirect reflexives (called also apparents or pronominal transitives). The verbal action does not "reflect" directly on the subject, but it takes place to their benefit, in their interest or by their initiative. The clitic pronoun does not represent in this case a direct object, rather some indirect complement «mi domando se ho sbagliato» (="I ask to myself", not "ask of myself", like in the direct reflexive); «mi lavo le mani».
In this case the usage of the reflexive voice indicates that the action is done to the benefit of the subject, as opposed to the case of Ho fatto una bistecca, where the steak could have been cooked for someone else.