Fox is the first woman to win the K1 and C1 double at U23 level, making up for the disappointment of last year when she won the C1 but failed to make the K1 final.
“It just felt really nice out there,” Fox said.
“I was a bit more relaxed today. I think having won the K1 I got some of the nerves out. For the C1 today I just felt like I should enjoy myself and make the most of the home championship.”
Fox had qualified fastest for the final, and sat back and watched the first nine competitors struggle with the difficult Penrith course.
Her closest competitor, fellow-Australian Alison Borrows, was set for a good result before capsizing heading into the final two gates.
The Czech Republic’s Monika Jancova finished second, 18 seconds behind Fox, while Australia’s Georgia Rankin produced her career best performance to finish 4th in the Women's C1 final narrowly missing a medal.
Fox said her results this week restored her belief that she is able to do both disciplines at a major event.
“After last year’s disappointment, to win both this year, on my home course with a bit more pressure, was awesome,” she said.
“I’m enjoying doing both, and having fun, so it’s been a really memorable weekend.”
Fox’s younger sister, Noemie, was unable to match the results of her sister, picking up three missed gate penalties to finish at the back of the junior C1 field.
France’s Lucie Prioux won the gold, just one point 18 seconds ahead of Czech Martina Satkova.
In the men’s competition, Italy’s Roberto Colazingari repeated his performance of two years ago to win gold in the U23 C1, while Germany’s Florian Breuer won the junior C1 gold.