The two are being tasked with being the creative hubs of the team under new manager Thomas Tuchel.
But the pair met for the first time in 2015, when they were playing in an under-17 England vs. Germany match.
"It was my first game on TV, playing against Germany, so it was a massive game for us at Rotherham's stadium," Mount told England's YouTube channel.
"I can't remember the final score, but I did score a goal in the game and that's what I remember - it wasn't too bad a goal.
"Kai Havertz, my team-mate at the moment, is actually in the video.
"Not many people know this, but he is the one that grabs my face. I've spoken to him about it at training and we had a good laugh about it.
"He actually remembered it as well. It was funny. Now he's going to get exposed now, so everyone is going to know. But great memories to score for your country."