Cherry compote filling

Cherry filling gives a cake the acidity that balances cream and chocolate. Its job is to stay put and not soak the sponge. The usual failure is a runny filling, and the cake slides because the fruit gave up its juice after assembly.

Ingredients and what each one does

• Cherries bring flavour and acidity. Fresh or frozen both work, but frozen cherries release more juice, so the filling takes longer to cook down.
• Sugar sweetens, helps preserve, and draws juice from the fruit.
• Cornflour (cornstarch) is the thickener. It only swells fully once it has boiled, so an undercooked filling stays thin.

How to make it

1. Put the pitted cherries and their juice in a pan with the sugar over medium heat and bring to the boil. The sugar dissolves into the juice as the fruit softens.
2. Mix the cornflour with a little cold water or juice first; dry starch dropped into hot liquid clumps. Pour it in a thin stream while stirring.
3. Simmer, stirring, for about 8 minutes after it boils, until clear and thick. The sign is that a spoon leaves a track that doesn’t close at once. Reaching a boil matters, because that’s what activates the starch.
4. Cool completely, first to room temperature and then in the fridge. Hot filling melts cream and soaks the sponge. A starch gel firms up fully as it cools, so hot filling should look slightly thinner than what you want in the cake.
5. Spread in an even layer inside a ring of cream, a dam that keeps the filling from squeezing out.

What can go wrong

• Runny. It never reached a boil, or there’s too little starch for the amount of juice. Return it to the heat with a spoon of slaked starch and bring it to the boil.
• Rubbery. Too much starch, or cooked too long.
• Cloudy. Normal for a starch-thickened filling; it won’t be glass-clear.
• Soaks the sponge. It went on warm or without a cream dam.

Substitutions

Potato starch thickens at a lower temperature and gives a clearer gel, but it doesn’t like prolonged boiling. Frozen cherries are fine: don’t throw away the thawed juice, but count it, because it thins the filling. A little lemon juice restores acidity if the fruit was sweet.

Storage

In an airtight container, up to a week in the fridge. It can be frozen, but may weep a little after thawing.