Mary Berry Watercress Sauce

The first time I made this sauce, I completely botched it. Thought I was being clever by simmering everything together from the start—ended up with a grey, sludgy mess that tasted like overcooked peas. Not the bright, fresh green I was after.

But I was determined. I’d made a gorgeous salmon en croûte and couldn’t bring myself to serve it with a sad dollop of mayo. So I started again. This time I changed the order, softened the shallots first, added the watercress off the heat, and blitzed the whole thing. And finally—success. A vibrant, herb-flecked sauce with just enough zing to cut through the richness of the fish.

If you’ve ever ended up with dull colour or bland flavour, let me show you how I fixed that.

Why This One Works So Well

Most watercress sauces fall into one of two traps: they’re either bitter from overcooked greens or too bland to hold up next to a main. This version avoids both.

• Shallots instead of onions give a softer base flavour that won’t fight the herbs.
• A handful of frozen peas adds colour and a hint of sweetness, without tasting like mushy peas.
• Crème fraîche gives creaminess without heaviness.
• And the real trick? Adding the watercress off the heat and blending quickly. It keeps that vibrant green and fresh peppery flavour.

Ingredients + Why They Matter

• Butter (20g) – For softening the shallot. I’ve tried oil, but it lost that mellow base note.
• Shallot (1, finely chopped) – Much gentler than onion. Keeps the sauce delicate.
• Plain flour (15g) – Just enough to thicken without making it stodgy.
• Vegetable stock (400ml) – I use a light, low-salt version so it doesn’t overpower the herbs.
• Frozen peas (100g) – This was a surprise win. Boosts colour and gives body.
• Watercress (100g, chopped) – The star. Add it off the heat to keep it lively.
• Crème fraîche (5 tbsp) – Adds creaminess and a slight tang. Doesn’t curdle like double cream.
• Fresh mint (1 tbsp, finely chopped) – Optional, but adds a pop of freshness.
• Salt and black pepper – Just enough to balance.

Making It Yours (Without Ruining It)

• No crème fraîche? Full-fat Greek yoghurt can work, but only if you don’t reheat it too much.
• No peas? I tried spinach—it dulled the colour and didn’t add the same sweetness. Not recommended.
• Want it richer? Stir in a splash of cream alongside the crème fraîche.
• Dairy-free? I tested with olive oil and a plant-based crème fraîche alternative. It worked, though the texture was thinner.

Mistakes I’ve Made (And How to Avoid Them

What Went Wrong	Why It Happens	How to Fix It
Sauce turned grey	Added watercress too early	Stir in off the heat and blend immediately
Sauce split	Boiled after adding crème fraîche	Reheat gently—never boil
Lacked flavour	Used water instead of stock	Always use vegetable stock, not plain water

How to Make Mary Berry’s Watercress Sauce

1. Melt the butter in a medium saucepan over medium heat. Add the chopped shallot and cook for 2 to 3 minutes until softened but not browned.
2. Stir in the flour and cook for 1 minute, stirring constantly.
3. Take the pan off the heat and slowly whisk in the vegetable stock. Return to the heat and cook until slightly thickened, like single cream.
4. Add the frozen peas and simmer for 2 minutes.
5. Remove from heat. Stir in the chopped watercress and let it wilt.
6. Blend until smooth—either with a stick blender or in a food processor. Return to the pan.
7. Stir in crème fraîche and chopped mint. Season with salt and black pepper. Reheat gently before serving.

Tips From My Kitchen

• I always add the watercress off the heat—learned that the hard way. It keeps the colour bright.
• If I’m making this ahead, I leave out the crème fraîche until just before serving.
• My stick blender does a better job than the food processor—it’s quicker and saves on dishes.
• If serving with something rich like salmon, go easy on the salt in the stock.

Storage + Serving

• In the fridge: Keeps for 2 days in an airtight container. Reheat gently.
• In the freezer: Freeze for up to 1 month. Defrost overnight in the fridge, then warm slowly.
• Serving ideas: Perfect with grilled salmon, salmon en croûte, or white fish. Also surprisingly good with roasted baby potatoes.

FREQUENTLY ASKED QUESTIONS

Q: Can I use fresh peas instead of frozen?
Yes, just simmer them slightly longer. But frozen works beautifully and is what I use.

Q: Do I really need to blend it?
For a smooth sauce, yes. If you like a rustic texture, you can leave it unblended—but it won’t be silky.

Q: Can I make this in advance?
Definitely. Just store in the fridge and reheat gently. Don’t boil once the crème fraîche is in.

Q: Is it okay to skip the mint?
Absolutely. It adds freshness, but the sauce is still lovely without it.

Q: Can I use this on something other than fish?
Yes—try it with roast potatoes, chicken, or even stirred through pasta. It’s surprisingly versatile.

Try More Recipes:

• Mary Berry Stuffed Chicken Thighs With Lemon Sauce
• Mary Berry Salmon And Herb Coulibiac
• Mary Berry Orange Sauce For Duck​
• Mary Berry​ Bread Sauce Recipe