Sahrawat said the key to success was to "keep evolving" what the restaurants were doing.
"We want to create stories of what New Zealand food is and showcase how amazing the food can be. It's not just Auckland, it's the whole country.
"Our aim is to show overseas and local diners what cuisine is. And that to us is what modern cuisine is."
At the beginning of the year, both restaurants ditched imported food and modelled their menu on seasonal New Zealand food.
He said it was "unbelievable for both restaurants to get those prizes. It is a testament to the teams".
Despite winning the supreme award in 2017 and 2016 he was surprised at the result on Monday night.
Metro editor and head judge Susannah Walker said the unprecedented number of awards was testament to Sahrawat's unquenchable thirst for perfection, dedication to his craft and attention to detail in every aspect of his restaurants.
The judging panel considered more than 100 contenders, refining the list to 50 after months of deliberation.
Judges visited restaurants anonymously and paid for their own meals.
The awards were announced by master of ceremonies Clarke Gayford at a red-carpet event at Auckland Museum.
Last year Cassia was awarded the 2017 Metro Peugeot Restaurant of the Year for the second consecutive time.
Winners
Metro Peugeot Restaurant of the Year 2018
Winner: Sidart
Runner-up: Cassia
Best chef
Winner: Sid Sahrawat, Sidart and Cassia
Restaurateur of the Year
Winner: Sid and Chand Sahrawat (joint), Sidart and Cassia
Runners-up: Sarah Conway, Melissa Morrow & Blair Russell, Ponsonby Road Bistro
Best New Restaurant
Winner: Cotto
Runner-up: Hugo's Bistro
Best Fine-Dining Restaurant
Winner: Sidart
Runner-up: Pasture
Best Smart-Dining Restaurant
Winner: Cassia
Runner-up: Cocoro
Best Inner-City Bistro
Winner: Hugo's Bistro
Runners-up: Culprit and Depot
Best City-Fringe Bistro
Winner: Ponsonby Road Bistro
Runners-up: Apéro and Cotto
Best Neighbourhood Bistro
Winner: Cazador
Runner-up: The Engine Room
Peugeot People's Choice Award for Best Destination Restaurant
Winner: Casita Miro
Best Service
Winner: Apéro
Runner-up: The French Café
Best Wine List
Winner: O'Connell Street Bistro
Runner-up: Pasta & Cuore
Best Drinks List
Winner: Pasture
Runner-up: Cocoro
Restaurant Personality of the Year
Winner: Prateek Arora, Cassia
Runner-up: Kaylee Yoshida, Prego
Best New Fit-out
Winner: Hugo's Bistro
Food for Good
Winner: Gemmayze St