Shawn Mendes... in Yiddish?

Does Shawn Mendes write all of his songs in Yiddish first before translating them to English?

Shawn Mendes appears on CBS's 'The Late Late Show' to promote his newest album. (The Late Late Show with James Corden/YouTube)
Shawn Mendes, the chart-topping singer and Canadian heartthrob, writes all of his songs in Yiddish first before translating them to English. Or does he?
As part of Mendes’s weeklong appearance on CBS’s The Late Late Show – to promote his newest album – the 19-year-old sat down on the couch with Mandy Patinkin, the legendary actor of stage and screen.
James Corden, the host of the show, asked Patinkin if he was familiar with Mendes’s work.
“I consider, in all honesty, I somewhat consider myself an aficionado,” said Patinkin, 65, who grew up in Chicago as the son of two Jewish immigrants from eastern Europe. “I study it, I love it, our family loves it.”
Patinkin – who starred in the 1983 film Yentl – jokingly continued, that “a lot of people are not aware” that Mendes – like famous composer Irving Berlin – “wrote first in Yiddish and then in English.”
As Mendes laughed and nodded, Patinkin added that “they’re beautiful, they’re beautiful in Yiddish.”
Patinkin then regaled the audience with a few lines of the singer’s hit song “Stiches” in the mama loshen, as the audience - and Mendes, sat in rapt attention.