Blaak executed a perfectly plucky solo move in the final lap of the 152 kilometre race, capping off a super strong performance from the Dutch team.
Garfoot beat home the bunch and last year's world champion Amalie Dedriksen for the silver.
Like Dedriksen last year, Blaak's win is surprising to some as both normally serve domestique roles for their top ranked trade team Boels-Dolmans. But like Dedriksen, Blaak made the most of the opportunity presented to her, attacking the leading group with around eight kilometres to go.
On this occasion the roles were reversed with Dutch team mates and leaders in their own right, Annemiek van Vleuten and Anna van der Breggen back in the chasing group, contributing nothing to help secure the win for Blaak.
"When I was down on the floor I thought my race was over," Blaak said. "I hoped to come back and work for the team but never expected this,"
"I felt this would be my only chance to become world champion. I looked behind me and couldn't believe it. I still can't believe it."
As expected the Dutch made the peloton work hard all race, which Australia with its full complement of seven riders was largely able to match.
— UCIWomenCycling (@UCIWomenCycling) September 23, 2017
After the fourth lap, Aussie Rachel Neylan joined Amy Pieters (Netherlands) and Hannah Barnes (Great Britain) in the first big move of the day, the trio gaining a 30 second lead over the bunch. At the end of the fifth lap, Gracie Elvin swapped jobs with Neylan in a new move, joined by Lucinda Brand (Netherlands). Elvin, Barnes, Pieters and Brand were away until just before the start of the seventh lap.
In another aggressive move from Great Britain, Dani King attacked on the second last lap, a move quickly countered by Australian Amanda Spratt, the pair joined by Elise Delzenne (France) and Janneke Ensing (Netherlands).
It was then Van der Breggen's turn to pounce, which she did on the penultimate climb of the newly famed Salmon Hill. Garfoot followed, both soon joining Spratt's group on the descent.
With 20 kilometres left to race, Blaak, Barnes and Audrey Cordon (France) escaped off the front, leading the bunch by 20 seconds at the start of the final lap with Australia's Sarah Roy bravely attempting to bridge. An attack on the final climb on Salmon Hill again from Van der Breggen saw Garfoot follow with Katarzyna Niewiadoma (Poland) and van Vleuten, the quartet finally catching Blaak, Cordon and Barnes.
Junior men's road race
Denmark's Julius Johansen executed a solo move early on the final lap of the junior men's 135 kilometre road race to beat home Italians Lucas Rastelli and Michele Gazzoli, and the bunch, by 51 seconds.
Sebastian Berwick was Australia's highest placed rider finishing 20th in the main bunch. Teammate Mitchell Wright was in a strong position in the bunch on the final lap but was involved in a crash in the final kilometre and finished 51st.