Butterfly pea flowers, lemon juice & sugar — Thailand's magic colour-changing drink
The butterfly pea flower (Clitoria ternatea) grows across Southeast Asia and has been used as a natural dye for centuries. In Thailand, it is called 'dok anchan' and appears in rice, desserts, and this famous colour-changing drink. The transformation from blue to purple-magenta when acid is added is one of the most visually dramatic moments in food.
The colour change is pH-sensitive — the more lemon you add, the more magenta it becomes. For a layered effect, float the concentrated blue tea on top of lemonade — the colour shifts as you stir. Butterfly pea flowers are available at Asian grocery stores and online. Add pandan leaves to the steep for a more aromatic tea.