Banh mi? In Hong Kong? You realise Hong Kong isn't Vietnam, yes?
They all look the same to you, don't they?
There's a Cambodian version of banh mi, actually, the name of which escapes me. But... don't. Just don't. Whilst Cambodian food has many joys, (the beef curry with termites being particularly splendid) their version of banh mi is fúcking rank.
No no no no, I won't have it, you can't eat pho and banh mi in Hong Kong, it's cutural appropriation of the most oppressively imperialist kind.
Pho should only be eaten in the shophouse in Ho Chi Minh City where the Tet offensive was secretly planned. If you're lucky, after your lunch the Mama-san will take you upstairs to show you the plotters' room as well as the chair Uncle Ho sat in when he visited after the war.