Watercress Soup (Soupe au Cresson)

French Watercress Soup

Watercress (cresson) is a favourite in France, particularly for this classic soupe au cresson. It's season runs from autumn/fall through spring, when you'll find large bunches piled high at French markets.

This is the simple watercress soup we make at home: fresh watercress, potato, onion and garlic cooked in stock, then blended until smooth. You can also use a leek instead of the onion - I often do, and it works beautifully.

The potato naturally thickens the soup without needing lots of cream, while the watercress gives it that distinctive fresh, peppery flavour.

Watercress Soup Ingredients

To get the best out of your watercress, I recommend not overloading on the ingredients. Keep it simple to appreciate its natural flavour. For this recipe, it's so good, I often double the quantities.

• Fresh watercress - use 200g (7oz) trimmed watercress leaves and tender stems. French bunches can be enormous - a typical bunch I use weighs over 400g before trimming! As bunch sizes vary, use the weight rather than relying on "one bunch".
• Potato - floury varieties are best for soup, such as Binje in France or King Edward, Maris Piper, Cosmos and Desiree. Use about 250g (9oz) peeled floury potato. The potato isn't just there for flavour: it naturally thickens the soup, so weighing it helps give you the right consistency.
• Onion - one medium onion adds sweetness without overpowering the watercress. Alternatively, use one leek - I tested it again this way and it's equally delicious.
• Garlic & nutmeg - please don't make it without nutmeg. It's the secret ingredient that works.
• Stock - use 750ml (about 3¼ US cups) chicken or vegetable stock. I've deliberately kept this in ml and cups rather than pints, as UK and US pint measurements differ.

How to Prepare Watercress for Soup

Wash the watercress well. If they're particularly gritty, wash in a bowl of water with a few drops of vinegar or in a sink of cold salted water.

Then remove the large, thick stalks. I keep the leaves and the fine, tender stems near the tips - otherwise preparing a whole bunch becomes a labour of love!

Most importantly, weigh the watercress after trimming. Bunches vary enormously in size, so "one bunch" isn't accurate enough for this recipe.

How to Make French Watercress Soup

First, gently soften the onion (or leek) and garlic. Add the diced potato and stock, cover and cook for about 10 minutes before adding the watercress.

The watercress goes in later so it only cooks for another 10 minutes. This helps retain its beautiful green colour rather than over-boiling it.

Once the potato is tender, blend until smooth and season to taste with salt, pepper and freshly grated nutmeg.

Adding the watercress later also avoids unnecessarily prolonged cooking while helping retain its fresh colour and flavour.

What Does Watercress Soup Taste Like?

Watercress has a distinctive fresh, peppery flavour, similar to other members of the mustard family. Cooking softens its raw pepperiness, but you should still be able to taste that unmistakable watercress character in the finished soup.

Potato rounds everything out without masking it, while a little nutmeg works particularly well with the greens.

How do you Make Watercress Soup Less Bitter?

Watercress is known for its fine, soft leaves and particularly spicy, bitter taste when raw. However, this bitterness subsides when cooked so there's no need to even add any sugar or sweet vegetables.

Once cooked in soup with a large floury potato and a little nutmeg, it even has a slight taste of cheese to it. Don't ask why but my daughters confirm they get that too!

It's so naturally vibrant green that there's no need to add any other green vegetable to it. That way you have it pure and simple: the taste is fabulous.

Can You Make it Ahead?

Soupe au cresson lasts in the fridge well covered for up to 3 days. Just cool it first before storing in the refrigerator.

Watercress soup freezes well. Freeze for up to 2 months, preferably in individual portions, then defrost thoroughly before reheating.
If the soup thickens after chilling, simply loosen it with a splash of stock or water.

What to Serve with Watercress Soup

French watercress soup goes well with light accompaniments, so not to interfere too much with its subtle flavours. Top with the little watercress leaves, stir or swirl a dash of cream or a wee dollop of crème fraîche. It's excellent paired with cheesy bread plus:

• A crusty baguette with either a little butter or dip into good olive oil.
• Leftover rice: like this carrot soup, add some rice if you prefer without potato.
• Surprise your guests with a mini savoury herb macaron
• Serve with fluffy cheese scones.
• Serve as mini soups as an apéritif with cheese biscuits or Parmesan crisps.
• Leftover soup? Use the rest of the soup to make a lush sauce, using the basis of this beurre blanc. Just replace the lemon with 3-4 tablespoons of watercress soup and pour over baked salmon, pork ribs or roast chicken.