Thịt heo kho trứng (or thịt lợn kho trứng, if you're from Northern Vietnam) is a rich pork belly, star anise and boiled egg stew that you tend to find pre-cooked in bain maries and aluminium pots in any Vietnamese market from Phu Quoc to Bac Ha. In series one of Food Safari, Nhut Hunyh, whips up his thit heo kho recipe for Maeve: he associates it with going home for Tet, the Vietnamese lunar New Year festival.

For a dish that is dead simple to prepare (Step 1. Marinate; Step 2. Boil), its flavour is rich, complex, highly variable and warmly aromatic. The palm sugar, fish sauce and soy sauces contained within can all be multifaceted flavours in themselves depending on how much money and effort you're willing to spend on acquiring good ingredients.

Using the roots of spring onion is something that I'd never done before, so I've taken to eating a few of them straight every time that I use a spring onion to see if their spring onion-ness is more concentrated than in the stalks. I haven't come to a definitive conclusion yet but still am shocked that nobody has ever pointed out to me before that I could be eating this, instead of sending it straight to the compost.

Thit heo kho is also a beautiful illustration of how any idea of a food being culturally and nationally authentic falls apart when under close scrutiny. Everyone steals each others' comfort foods.

In Cambodia, you'll find an identical dish, khor sach chrouk at roadside stalls; in Thailand, you'd chow down on an interchangeable muu phalo. Just like in Vietnam, all nations with a taste for caramelized meat in a hotpot make variations on the same dish. Thai-based food photographer Austin Bush, for example, documents a goose-filled haan phalo sans eggs in Bangkok. The Thai brand, MAMA, even produces an instant noodle in phalo flavour. Vietnam too, has a host of kho dishes available with most imaginable proteins.

The ingredients soy sauce and star anise (and the even spread of the dish across South East Asia) hint that the dish has a much older Chinese origin. David Thompson's flamingo pink tome Thai Food suggests that muu phalo made it into Thailand in the 1800s with the wave of Chinese migration, although given the wide geographic coverage, this food may have been introduced from Southern China into Vietnam and elsewhere even earlier.

If there is a common element within comfort foods that transcends national tastes, I'm not sure what it is. Any suggestions?