'Mentality monsters' was the label given to Chelsea after years of success under previous manager Emma Hayes - and they have built on that with Bompastor.
"We stick to the facts," was the message from the Blues boss this week as she reminded her players there was plenty of time for them to bounce back from last week's 2-0 first-leg defeat.
Their belief and composure was evident in abundance as they refused to take their foot off the gas and maintained the pressure on City.
Chelsea were far superior in every department as Baltimore, Bjorn and Ramirez made City pay in a relentless first half, and the visitors never recovered.
The lack of depth in the City squad was on show, with only four outfield players on the bench due to a long list of injuries which meant options to switch things up were limited.
It felt like a mountain to climb and, although City improved in the second half, Bompastor's side looked comfortable defending their lead.
City have shown improvements during Nick Cushing's short time as interim manager, but this was the ultimate test against England's serial winners and they fell short.
"It's difficult for me to say where we're at because we have had so many key players missing - but that is not an excuse," Cushing said.
"I am proud of the group. We have shown the togetherness and fight and spirit is there. We have caused Chelsea real problems in all four games."
Meanwhile, Bompastor has managed her squad perfectly, rotating players and making shrewd substitutions throughout the last two weeks in order to win the matches they needed.
"I said after the first leg, we were alive and we knew it would be possible," she said. "We put a lot of energy as staff to make sure the plan was the right one.
"You never know until you play the game but I felt the plan, our body language and the way we showed the players we were confident going into this game was the right thing to do."
Bompastor won the Champions League as a player with Lyon before leading them to glory as a manager, and her experience in this tournament could prove to be crucial as Chelsea bid to lift the trophy for the first time.
Their task will not be an easy one as they face defending champions Barcelona in the semi-finals for the third season in a row - having been beaten on both previous occasions.