Simple Strawberry Cake Filling
Fresh strawberries between cake layers look wonderful and, an hour later, leak. Cooking the fruit down with a little cornflour fixes that: you get a filling that holds its shape, tastes strongly of strawberry and stays where you put it. Cooling it properly is not optional.
We would rather show you nothing than show you the wrong thing. A picture of a finished cake here would suggest this recipe makes a cake, and it does not.
- Prep time
- 10 minutes
- Bake time
- 10 to 12 minutes
- Total time
- About 2 hours including cooling
- Makes
- About 350g, enough to fill one 20cm two-layer cake
- Difficulty
- Beginner
Ingredients
- 400g strawberries, hulled and chopped
- 80g caster sugar
- 1 tbsp lemon juice
- 2 tbsp cornflour
- 2 tbsp cold water
Equipment
- Small heavy-based saucepan
- Wooden spoon or heatproof spatula
- Small bowl for the cornflour
- Shallow dish or tray for cooling
- Airtight container
Method
- Put the strawberries, sugar and lemon juice in the pan over a medium heat.
- Cook for 5 to 6 minutes, stirring, until the fruit has broken down and released its juice. Crush it against the side of the pan if you want a smoother filling, or leave some pieces whole.
- Stir the cornflour and cold water together in a small bowl until completely smooth. Never add dry cornflour to a hot pan: it will go lumpy and the lumps will not come out.
- Pour the cornflour mixture into the pan, stirring constantly.
- Bring to a gentle bubble and cook for a further 1 to 2 minutes, still stirring, until it thickens and turns glossy. It should coat the back of a spoon and hold a line when you draw a finger through it.
- Take it off the heat. It will thicken further as it cools, so stop while it still looks slightly loose.
Cooling
Spread the filling into a shallow dish so it cools quickly and evenly, cover the surface with cling film to stop a skin forming, and leave until it reaches room temperature. Then chill for at least an hour. Warm filling will melt buttercream, soak into the sponge and slide the layers apart. Cool it fully or do not use it.
Storage
Keep in an airtight container in the fridge and use within 3 days. It also freezes for up to 3 months; defrost in the fridge overnight and stir before using. Because it contains fresh fruit and no preservative, a cake filled with it must be kept refrigerated.
KKD baking tips
- Pipe a buttercream dam. Pipe a ring of firm buttercream around the edge of the bottom layer and spread the filling inside it. This is how bakeries stop fruit fillings squeezing out, and it takes ten seconds.
- Keep the layer thin. Two or three millimetres is plenty. A thick layer of any wet filling will soften the sponge underneath it.
- Chill the filled cake for 30 minutes before you cover it. The filling sets and the layers stop moving.
- Do not skip the cornflour and simply cook the fruit down. Reduced fruit is still a liquid; the starch is what holds it.
- Taste before it cools. Strawberries vary a lot. Add a little more sugar or lemon while it is still in the pan.
Common mistakes, and how to fix them
- Soggy layers: filling used warm, spread too thickly, or no buttercream dam.
- Lumpy: dry cornflour went into the hot pan instead of being slaked with cold water first.
- Too runny once cold: it did not reach a proper bubble after the cornflour went in. Return it to the pan and cook another minute.
- Too stiff: a little too much cornflour. Beat in a tablespoon of water while it is still warm.
Serving suggestions
Lovely between vanilla or chocolate layers, with vanilla buttercream on the outside, and good spooned over the Classic Vanilla Celebration Cake served as a dessert.