This silky, tangy Mary Berry Lemon Posset is made with double cream, caster sugar, and fresh lemons, and ready in just over 3 hours. The magic happens when the hot sweetened cream reacts with the citrus juice, thickening into a velvety custard without any gelatin. I find this to be the most reliable make-ahead dessert for entertaining guests.

Why This Classic Works

Lemon posset works because of a specific chemical reaction between the casein proteins in the cream and the acid in the lemons. The first time I made this, I panicked because the mixture looked far too thin in the pan, but patience is key as it firms up beautifully in the fridge. It eliminates the need for eggs or cornflour, giving you a much purer, cleaner cream texture.

The secret to Mary Berry’s version is the precise boiling time. Simmering the cream and sugar for exactly three minutes concentrates the liquid just enough to ensure a perfect set. If you under-boil it, the posset remains runny; over-boil it, and the texture can become grainy, so I always set a timer the moment it starts bubbling.

Mary Berry Lemon Posset Ingredients

600ml double cream
150g caster sugar
2 large lemons (juice and zest)

How To Make Mary Berry Lemon Posset

Dissolve the Sugar: Pour the double cream and caster sugar into a large saucepan. Place it over low heat and stir gently until you can no longer feel the gritty sugar crystals on the bottom of the pan.
Simmer the Mixture: Turn the heat up to medium and bring the cream to a lively simmer. Let it bubble for exactly 3 minutes, adjusting the heat so it doesn’t boil over, then remove the pan from the hob.
Add the Citrus: Allow the cream to cool for 5 minutes before whisking in the lemon juice and zest. If you add the juice while the cream is boiling hot, it may curdle immediately.
Pour and Chill: Divide the mixture evenly between 6 ramekins or small glasses. Cool to room temperature, then refrigerate for at least 3 hours (preferably overnight) until firm.

Recipe Tips

Watch the boil: Double cream rises rapidly when it boils. Use a larger saucepan than you think you need to prevent a messy overflow on your hob.
Cool before chilling: Never put the hot ramekins straight into the fridge. Let them reach room temperature first to prevent condensation from dripping back onto the surface of the posset.
Texture preference: Mary Berry usually leaves the zest in for texture. If you prefer a completely smooth mouthfeel, strain the mixture through a fine sieve before pouring it into the glasses.

What To Serve With Lemon Posset

The creamy richness of a posset needs a crunchy element to provide contrast. I almost always serve this with thin, buttery shortbread biscuits or almond thins on the side. Fresh raspberries or a compote also work wonderfully, as their sharpness cuts through the heavy cream.

How To Store

These possets are excellent for making ahead and will keep in the fridge for up to 3 days. Cover each glass tightly with cling film to stop them from absorbing other fridge odours. Freezing is not recommended as the cream will split and lose its silky texture upon thawing.

FAQs

Why didn’t my posset set?
This usually happens if the cream wasn’t boiled long enough or if the lemons weren’t acidic enough. Ensure you simmer for the full 3 minutes and use fresh lemon juice rather than bottled.

Can I use single cream or milk?
No, you must use double cream (heavy cream) with a fat content of around 48%. Lower fat dairy products do not have enough fat structure to set with the acid reaction.

Can I use limes instead?
Yes, lime posset is delicious. You will likely need 3-4 limes to get the same amount of juice as 2 large lemons, but the method remains exactly the same.

Nutrition

Calories: 540 kcal
Total Fat: 48g
Saturated Fat: 30g
Cholesterol: 130mg
Sodium: 40mg
Total Carbohydrate: 28g
Protein: 2g