The special weed which is the secret to the distinct fresh aroma of Southeast Asia cuisine.
My mom brought some from Malaysia in June and they are now thriving in my garden. After going through all this trouble, I just discovered the Vietnamese lady selling beef pho in Dulan has a huge patch growing in her backyard!
Here’s a description from Wikipedia
Persicaria odorata, the Vietnamese coriander, is an herb whose leaves are used in Southeast Asian cooking. Other English names for the herb include Vietnamese mint, Vietnamese cilantro, Cambodian mint and hot mint. The Vietnamese name is rau răm, while in Malaysia and Singapore it is called daun kesom or daun laksa (laksa leaf). In Thailand, it is called phak phai (ผักไผ่) and the Hmong word for it is luam laws. In Laos, it is called phak phaew (ຜັກແພວ.)
It is neither related to the mints, nor is it in the mint family Lamiaceae but the general appearance and odor are reminiscent. Persicaria is in the family Polygonaceae, collectively known as smartweeds or pinkweeds.