What are the differences between these two types of basil that is so prominent in authentic Thai dishes?
Thai basil is the sweeter of the two and grows on purplish stems, topped with pretty, reddish purple flower buds. The flowers are edible and both leaves and flowers are sweetly perfumed with a mix of a distinctly basil scent--that of anise or licorice. As such, it is sometimes referred to as "anise basil" or "licorice basil," but are not to be confused with the Western version.
You can put handfuls of Thai basil in dishes. It is used in everything from curries, salads, soups and stir-fry.
Holy Basil, or also known as Hot Basil, is spicy, not sweet. There are two varieties: a white (light green) and a red, which has a reddish purple cast around the stems and the underside of darker green leaves. The lightly hairy leaves of both kinds are jagged along the edges and are smaller and more fragile than Thai sweet basil.
The peppery combination of zesty mint and basil flavors of Holy Basil enhance when cooked and therefore, it is better to use this type of basil cooked than to eat it raw. It is mostly used in simple stir-fries and the famous Pad Ke Maw.