The stars appear together in Derek Cianfrance's upcoming crime drama The Place Beyond The Pines, which also stars Bradley Cooper, Rose Byrne and Ray Liotta.
"I have never felt so creatively satisfied on a film," Mendes told Marie Claire of working with Gosling."
She added that the actor, who is her reported boyfriend, was "amazing" and a "dream co-star".
Quizzed on her romantic relationship with the Drive star, she added: "Stop, just stop! I'm not gonna budge. I feel uncomfortable talking about it. It's too personal.
Pushed on whether she wanted marriage and children, she said: "Those are such boring topics to me.
"I don't like talking about things that I want in the future, because I feel by verbalising things, they won't come true."