The operator of two Melbourne La Porchetta restaurants who paid more than 100 young workers in pizza and soft drink has been fined $335,000 after an investigation by the federal workplace watchdog.

Ruby Chand, who runs two of the pizza chain's franchises in Pakenham and Berwick in the city's south-east, was found to have underpaid 111 teenage workers more than $250,000 over four years.

The Federal Circuit Court heard Chand had paid young cooks, kitchen hands and waiters below minimum wage and withheld annual leave entitlements. A number were employed under training programs which enabled Chand's companies to claim more than $45,000 in Commonwealth benefits.

The court was told that Chand, of Tecoma, had claimed the employees were given half-priced pizza and soft drink, which was being "offset" against their wages and entitlements.

"Such a practice belongs in the dark ages," Judge John O'Sullivan said.