Celtic claimed the trophy for the fourth time in a row with a 1-0 victory over Kaizer Chiefs at Free State Stadium on Sunday.
The 18-year-old Mabaso decided matters with a composed finish in the 62nd minute after he out-paced experienced defenders Morgan Gould and Siyanda Xulu.
"He is only 18 years old. He only matriculated last year," says Larsen.
"This is his second season in the first team. He is starting to show signs of maturity and starting to feature in the first team.
"You saw the composure of someone who is 18 years and beat both Morgan Gould and Xulu to score that goal.
"I am happy with the progress he has shown so far."
Meanwhile, Larsen feels Phunya Sele Sele showed they mean business on the weekend.
"This was a clear message to try and show consistency and keep on working hard," Larsen says.
"We still remain unbeaten in five games in the League and we must keep on doing more. I have said it before that this League is difficult and we must keep on working hard.
"Our next game is against Arrows and we should try to get points in every game we play and a draw should be the worst case when we play away."