In a medium-sized saucepan, bring the milk and the chopped lemongrass to a boil. Let this naturally cool down and infuse in the saucepan for about 20 minutes. Puree this mixture in a strong blender or with an immersion blender. Strain the mixture with a chinois or a fine strainer. Re-measure the infused milk weight to 480g. If you need more liquid, simply add more milk.<