Union defeated Club Brugge 5-4 on penalties after a 1-1 draw, with Mofokeng handed the winning moment as he rifled his spot-kick in off the underside of the bar.
It is a sign of how quickly he has settled in Belgium that he was both asked by coach David Hubert to take the crucial fifth penalty and had the confidence to bury it.
“I’m happy because I won my first cup here. I’m excited for everyone. They (his teammates) were there for me to boost my confidence. My teammates are the best, and that is why we won this cup,” Mofokeng told his club’s media.
“Coach Hubert came to us and told us who was taking the penalties. They saw me taking penalties in training, and it boosted my confidence to be asked, which is high now. We can keep on going.”
But Mofokeng, 21, did admit to some nerves as he stepped up to take the kick.
“When I put the ball down, I was very scared because he (Club Brugge goalkeeper Yann Sommer) is a big man. He has played for very big teams,” the Bafana Bafana attacking midfielder said.
“You just need confidence in these types of games, and I kicked the penalty with that confidence. That is why I scored.”
He performed a trademark dance celebration and was joined by several of his new teammates.
“It is about celebrating. In South Africa, we have those dances, so I just thought about home. We already did it in training, so I think they (his teammates) know it already.”
Nicolo Trosoldi put Brugge in the lead four minutes into the second half as he volleyed home from an acute angle at close range, but the match went to penalties after Union’s Argentine centre-back Kevin Mac Allister equalised with 13 minutes remaining.
Every penalty in the shoot-out was converted except that of Cheveyo Tsawa, the teenager newly signed from FC Zurich, whose effort was saved by Union goalkeeper Vic Chambaere.
It was Union’s second Super Cup triumph after they also defeated Club Brugge two years ago.
Union are next in action against Norway’s Bodø/Glimt in the UEFA Champions League third qualifying round on Tuesday.