Berry confit

Berry confit is a thin, bright layer that adds acidity and fruit flavour between sweet sponge and cream. Its most common failure is leaking: the filling squeezes out of the cake or soaks the sponge. The cause is usually water that was never bound, not too little sugar.

Ingredients and what each one does

• Strawberries give body and sweetness. They are low in pectin and about 90% water, so on their own they make a runny result.
• Raspberries bring acidity, aroma and natural pectin, a gel-forming fibre that helps the confit set. This is why the pair works better than strawberries alone.
• Caster sugar sweetens and binds water, so the fruit stays glossy and does not weep. It dissolves faster than coarse sugar, so there is no gritty feel.
• Starch (the site’s quick method uses a little) is the safety net. Starch granules swell in hot liquid and hold water in a gel.

How to make it

1. Cut the strawberries small and combine them with the raspberries and sugar. Rule of thumb: small pieces release juice and soften evenly. Sign: the fruit sits in its own syrup. Leave 10 to 20 minutes.
2. If you use starch, stir it into the sugar first. Starch dispersed among sugar crystals does not clump when it meets liquid. Sign: no dry white specks when you stir.
3. Heat over medium heat, stirring gently. Heat drives out water and breaks down the fruit. Sign: the berries slump and the syrup turns glossy.
4. Boil for 1 to 2 minutes. Starch only thickens fully at a near boil. Sign: bubbles break slowly and a spoon leaves a trail that closes lazily.
5. Take it off the heat and cool completely, covered with cling film touching the surface to prevent a skin. Starch gel keeps firming as it cools. Sign: a spoonful on a cold plate holds its shape. Allow 1 to 2 hours, or less in the fridge.

If the cold test is still loose, boil it again briefly. Do not judge thickness while hot.

What can go wrong

• Leaks from the cake. Too much free water, or the filling was spread warm. Cook it until thick and use it cold, with a ring of cream around the edge.
• Soaks into the sponge. The sponge is dry and thirsty, and the filling is thin. Thicken the confit before changing anything else.
• Thins out after cooking. Over-boiling can break starch down, especially with acidic fruit. Keep to 1 to 2 minutes at the boil.
• Dull colour and jammy taste. It was cooked too long. Fresh flavour fades with extended heat.

Substitutions

• Frozen berries work, but they release more water. Cook a little longer and check with the cold-plate test.
• Seeds: straining out the raspberry seeds is a matter of taste. Try it both ways and weigh the result.
• Sugar level: how sweet you go is also taste. Under-sweetened confit sets less firmly, so check the cold test again.

Storage

In a closed jar in the fridge for up to about 5 days (our estimate, so judge by smell and look). Stir before using. Once spread in a cake, it should stay chilled.