Boil the smashed lemongrass in water and let it reduce. Strain and keep the infused water and lemongrass.

Saute sliced shallots until caramelized.

Add the sliced and smashed lemongrass until fragrant.

Mix in dijon mustard and sauteed until ingredients mix well together.

Add the water and cream together and bring it to boil in high heat. Turn the heat to medium and let it simmer for 10 minutes until it thickens.

Put in the seasoning and stir well. The sauce is ready to serve!