Mostert was spectacular in the Darwin Triple Crown opener with a charging recovery from a poor showing in qualifying on Friday.
He was able to convert his 22nd spot on the grid to fifth at the end of the 48-lap race in an effort that deeply impressed WAU CEO Stewart.
“That was really special,” Stewart told Speedcafe. “He was unbelievable.
“I’ve got to say, the crew and the engineers did a great job giving him the opportunity to do that, but man, he drove the wheels of it.
“It was really cool and the feeling of the garage was great. There’s nothing like hope. When you’re moving forward and you’ve got that feeling of momentum, it’s amazing for the team and the fans.
“I could hear some of the commentary and they were giving it a big rap as well, which is great. People could see something special was happening out there.
“I have to preface it with the fact we didn’t do the job we needed to do in qualifying. You look at that and go, okay, we need to find that one-lap pace.
“But wow, it was a good race car. The team did a great job. The pit stops were mega. They were two epic stops to help deliver that result.
“And then to have a driver like Chaz, you feel lucky and privileged to have someone like that in the team.
“He puts the team on his shoulders. He did one a few years ago when we went to the back off the grid with a penalty at Sydney Motorsport Park. He got in the car and said ‘watch this’ and then he got to second.
“But that today was really special, because there weren’t people falling off the track in front of him. He passed all of those cars off his own merit.
“He is a special driver and it was a great reward for him too.”
The only downside, according to Stewart, is a sense of frustration that qualifying didn’t go better, given the speed in the race.
“In hindsight, you look at it tonight and think what could have been if we’d qualified near the front,” he said. “And that’s where we need to be, we need to be fighting at the front.”
Stewart likened the recovery to the Darwin Triple Crown effort in 2022, when Mostert was disqualified on the Saturday for illegal use of a cooling fan on the grid, and then scored victory on the Sunday.
That, says Stewart, is still his favourite win from his time at WAU.
“We had a moment here a few years ago where we got [disqualified] on the Saturday for a mistake on the grid. And we won on Sunday,” he said.
“I still put that up as my favourite win. I love all the Bathurst wins, but when you’re down and you feel like things aren’t working, and the team knuckles down and he pulls out a result like that… he did it that day, and he did it again today.
“It is bloody epic. I can’t speak highly enough about him. He’s a bloody beauty.”