From the Wikipedia page
Vietnamese lotus tea (Vietnamese: trà sen, chè sen, or chè ướp sen) is a type of green tea produced in Vietnam that has been flavored with the scent of Nelumbo nucifera. It is a specialty product of the Vietnamese tea industry and is consumed as part of celebratory events or festivals.
The tea is made by allowing the green tea to absorb the flower's natural scent. This is done through several methods:
- Stuffing green tea leaves into a flower and leaving them overnight
- Pulling the entire stamen from the flower or just their anthers and then either
- Putting them overnight in a jar together with the tea leaves
- Bake the tea leaves with them
These steps can be repeated multiple times to increase the floral scent in the tea leaves. In the case of higher quality teas, one thousand lotus flowers per kilogram of tea are needed to complete this ancient process. Many modern production tend towards flavoring or perfumes to scent the tea.
Lotus teas are typically very potent and are best brewed for under 2 minutes using cooler brewing temperatures (160°F/70°C). Some fanciers will brew 3-4 times from one set of leaves.