Canadian Prime Minister Justin Trudeau had Rosh Hashanah dinner with someone who knows a thing or two about eating ... the dude from "Epic Meal Time"!

Harley Morenstein and Trudeau are fellow Canadians and family friends. As the Jewish half of the duo, it fell on Harley to teach the PM all "aboot" the holiday. We're told Trudeau joined the party at Harley's brother's house in Ottawa ... and dug into apples and honey, Challah bread ... the whole nine.

JT had a front row seat for the blowing of the shofar, but passed on blowing it himself. Still, wine, laughs and based on the pics ... a wonderful time with a nice Jewish family.