Saw Tooth - Ngò Gai
Tastes like intensive coriander. Commonly used as a garnish in phở or with beef salad. If you can not get hold of this, use coriander.
Basil - Húng Quế
Used as a garnish in noodle soups like phở and bún bò Huế. The aniseed aroma and flavour is liquorice like and translate in Vietnamese as cinnamon basil. The leaves originating from Thailand and Vietnam oxidizes very quickly but are more fragrant and contains more flavours than others.
Betel Leaves - (Lá Lốt)
Not to be confused with betel nut chews, lá lốt has a pungent, minty, peppery taste and smells rather like cinnamon. These heart shaped leaves are usually used as wraps for garlicky beef recipes or in salads. substitute with shiso/ perilla leaves or vine leaves
Earthy and bold yet very pleasant in peppery, cinnamon and fennel flavours. Often purple on one side and green on the other, it resembles stinging nettles. Also known as Japanese shiso or wild sesame. It is rich in omega-3 fatty acids, vitamin A & C, containing minerals calcium, iron and potassium. It is commonly used in China as medicine. Tía Tô is used in salads and summer rolls and cold bún noodle dishes. Subsititute with Japanese shiso or mint.
Delicate Kinh Giới resembles minty lemon balm and used in summer rolls, salads, fish and chicken dishes as well as garnishes in noodle soup such as bún bò Huế. This is great in a tea, just seep in boiling water for a refreshing and soothing drink in the sun. Use lemon balm if you can not find cockcomb - also known as Vietnamese lemon balm.
The citrus coriander odour is reminiscent but it is not related to the mint family. There is a spicy and peppery after taste that lingers. Also known as Vietnamese coriander or Vietnamese mint. It is commonly eaten fresh and raw in salads, gỏi cuốn, as well as in some soups such as canh chua and bún thang, and stews, such as fish kho tộ.
Garlic Chives - (Lá He)
Also known as Chinese chives. Tastes very garlicky and used as a seasoning in soups like won ton, salad and summer rolls.
Coriander - (Ngò)
Fragrant, diverse and wonderful! Coriander is used liberally as a garnish, torn or chopped over salads or almost any dish! Readily available in supermarkets, corner shops. A lot of the flavour is in the stalk.
Growing Your Own Tip:
You can perhaps buy seeds to grow your own herbs but I found hot mint in Columbia Flower market. It grew easily and in abundance in the summer. However, if you buy bunches of hot mint, basil, perilla and cockscomb in the shops, look out for a bunch with the thickest stalks. Once you have used the leaves, keep the stem in a glass of water (make sure its a glass so that you can see if you need to refill) you will see roots appear after 5 - 7 days. Remove from water and plant into a pot of soil and grow in a sunny spot. Hot mint, cockscomb and perilla grow very easily. You'll need very green fingers for basil but it does work.
Fresh herbs are imported in London on Thursday which is the best day to buy them. Always seek a bunch that is not bruised or too damp.
You can store herbs, dry from moisture in an air tight bag in the fridge. Apart from coriander most can last for up to 10 days. I've never tried freezing them.
Check out Luke Nguyen's guide to herbs here it also has medicinal uses.
Here is Andrea Nguyen's guide.
I will post another selection of herbs and spices. As for chillis, they are hot - so don't touch them and rub your eyes : )