An eventful match in north London saw Spurs run out winners thanks to second-half goals from Bergwijn and Heung-Min Son after Oleksandr Zinchenko had been sent off.
Mourinho told reporters that Bergwijn's goal, scored with his first shot on target in the Premier League, capped a fine display from the 22-year-old Netherlands international.
"It was a debut goal that was the icing on the cake of a very good performance," he said. "Independent of the goal I would say his performance was very good, very solid. Very mature. We worked hard during the week."
Bergwijn said it was a dream to open his account for his new club on his first appearance:
The match also saw plenty of controversial incidents that were referred to VAR. Raheem Sterling escaped a red card for a late foul on Dele Alli, while Manchester City were awarded a penalty after a VAR check.
Ilkay Gundogan saw his spot-kick saved by goalkeeper Hugo Lloris, but the France international then appeared to foul Sterling as he attempted to net the rebound:
Mourinho spoke about the incidents after the game and offered his opinion of VAR:
"I love football and I thought I was going to love VAR, that was my initial feeling. I love the truth... playing for three minutes and then after three minutes, the VAR gives a penalty, then if it's a penalty no problem. We can wait 10 minutes. I just want the truth.
"I thought I was going to love VAR the way I love goal-line technology. I love goal-line technology because there is no mistake. The VAR has too many mistakes, too many."
The win gives Tottenham's hopes of finishing in the top four a boost. Mourinho's side have moved into fifth place above Manchester United, Wolverhampton Wanderers and Sheffield United and are just four points behind Chelsea.