Remove outer dry leaves and cut off both ends of lemongrass. Bruise the lemongrass using a mortar and pestle ( or by using a spoon and chopping board) then cut the lemongrass so that it fits into the mug.
Peal and cut the ginger into small cubs and place in mug along with the mint leaves.
Pour boiling water into the mug and let lemongrass, ginger, and mint steep in the water for a few minutes.