These coriander roots are also known as Chinese parsley roots or cilantro roots. Though I use all parts of the coriander plant including the seeds and the leaves for cooking, the coriander roots are what I like to use most.
They are not only more aromatic and intense flavoured than the leaves but also have a nice, earthy, peppery and citrusy flavour. When I first ventured into Thai cooking, I would desperately look out for only the fat, old roots of the matured coriander plant. It took me months before I realized that the younger looking coriander plants have more flavourful and aromatic roots!
Do you know that the coriander plant is high in antioxidants and Vitamin C and that it can help to lower blood pressure a little?
I usually freeze the coriander roots whenever I buy coriander leaves for cooking. Before freezing, I will remove and discard as much of the fine roots. To use the coriander roots in cooking, just wash and bash them lightly with the back of a heavy knife and throw the roots into your pot. Slice or mince them and stir fry with your vegetables or meat. My mum used to throw in a few smashed coriander roots into jar of local achar (pickled carrot and cucumber) or pound coriander roots with garlic and make a rasam (a spiced South Indian soup) out of it.
So, what happens if you cannot find coriander roots for your Thai cooking? Use 6-7 coriander stems as substitute!!