Trim, peel, and quarter <quantity>1</quantity> onion

Trim <quantity>1</quantity> carrot and cut it into big chunks

Cut <quantity>¼</quantity> of a peeled celeriac into big chunks

Add <quantity>1<unit>tbsp</unit></quantity> of sunflower oil to a large pan over medium heat. Add the leftover heads and shells of <quantity>5</quantity> langoustines

Add the chopped vegetables and stir with a spoon

Add <quantity>1<unit>tbsp</unit></quantity> of tomato purée and mix it. Let it cook until the shells and vegetables start caramelizing

Add <quantity>2¼<unit>cups</unit></quantity> of water and mix it

Turn the heat down to low and let it simmer for 20m until the vegetables are tender

Place a clean kitchen towel on top of a saucepan with a mesh sieve, and strain the soup

Lift the fine mesh sieve to make sure all the liquid has been strained. Discard the shells and vegetables

Add <quantity>1</quantity> star anise to the soup. Add the juice and the bagasse of <quantity>¼</quantity> lemon, and set aside for 5m to infuse flavors

Remove the star anise and the lemon

Season with salt to taste and mix. The langoustine bouillon is ready

Enjoy this delicious and warming soup!