Easy Modern Plum Louise Cake with Swiss Meringue Topping
This modern twist on the beloved New Zealand classic, Louise Cake, combines a buttery lemon-zested shortcake base with a vibrant plum filling and a cloud-like Swiss meringue topping. The tender shortcake pairs beautifully with the tart-sweet plums, while the glossy, marshmallowy meringue adds a touch of elegance. The omission of coconut (usually mixed into the meringue layer) keeps it smooth and buttery while the bake on the meringue keeps a nice crunch on top. This is my little update on the NZ classic.
Ingredients
For the Shortcake Base:
180g butter, softened
200g sugar
1 egg
1 tsp vanilla extract
320g all-purpose flour
2 tsp baking powder
Zest of 1 lemon
For the Plum Filling:
225g plums (fresh or frozen), diced into 1.5 cm pieces
¼ cup (50g) sugar
1 tsp lemon juice
For the Swiss Meringue Topping:
115g egg whites (about 4 large egg whites, but it is best to measure by weight - See note at bottom). Ensure there are no yolk in them. Top tip: Break each egg white into a bowl separately, and then if it is clean of yolks tip it into your measuring bowl. Repeat the next egg into the first bowl, and so on. This will save you frustration if one of your whites gets yolk in it because you can set it aside for another use later (eg. scrambled eggs) and you won’t have tainted the rest of the whites you had already measured.
200g caster sugar
Method
Prepare the Plum Filling:
In a medium saucepan, combine the diced plums, sugar, and lemon juice. Cook over low-medium heat, stirring occasionally, until the fruit softens and releases its juices (about 5–7 minutes). Once the juices seem to reduce by half, mash the fruit with a potato masher.
Allow the mixture to simmer 1-2 minutes until slightly thickened. The plum mixture should be juicy but not runny. Remove from heat and let it cool completely.
Make the Shortcake Base:
Preheat your oven to 180°C (350°F) and line a 9x9-inch (or similar) baking pan with parchment paper.
In a large mixing bowl, cream the softened butter and sugar together using a hand or stand mixer until light and fluffy (about 2–3 minutes).
Add the egg, vanilla extract, and lemon zest and beat until fully incorporated.
In a separate bowl, sift together the flour and baking powder. Gradually add the dry ingredients to the creamed mixture, mixing just until combined.
Press the dough evenly into the prepared baking pan to form a smooth base.
Assemble the Slice:
Spread the cooled plum filling evenly over the shortcake base.
Prepare the Swiss Meringue Topping:
Wipe down your heatproof bowl with a little white vinegar and a clean paper towel (use a stand mixer bowl without the handle, or the bowl you will beat your meringue in with a hand mixer). This will ensure there is no fat residue in your bowl which can stop your egg whites whipping.
Place the egg whites and caster sugar in a heatproof bowl over a saucepan of simmering water. Whisk constantly until the sugar dissolves and the mixture feels warm to the touch (about 65°C or 150°F). You can check that the sugar has fully dissolved by pinching some of the mixture (careful it is hot) between 2 fingers, If it feels smooth and you can’t feel any sugar crystals then it is ready (see troubleshooting below).
Remove from the heat and transfer the mixture to a stand mixer fitted with the whisk attachment. Whip on high speed until stiff, glossy peaks form and the mixture has cooled to room temperature (about 5–7 minutes). Stiff peaks will hold their shape on the whisk when pulled out of the bowl as shown in the video above.
Spread the meringue evenly over the plum filling, creating decorative swirls if desired (although try not to have very high peaks as these will cook much faster than the rest of the slice and may brown too much). I find it is easiest to dollop large spoonful's all around the tray, and then gently smooth with the back of a spoon or a palette knife, pushing sideways to spread the bulk of the meringue rather than downwards. This keeps the meringue white and not dotted with plum.
Bake:
Bake the assembled slice in the preheated oven for 25–30 minutes, or until the meringue is set and lightly golden. Every oven is slightly different so keep an eye on it in the final few minutes of baking. You will smell the sugars on the top of the meringue starting to just caramelise and go slightly brown.
Allow the slice to cool in the pan before removing.
This slice is best on the day it is made as you get the crunchy top of the meringue with the softer marshmallowy meringue underneath. However, I have still enjoyed a piece if any of it manages to make it to day 3! Just be sure to store it in an airtight container for up to 3 days.
Troubleshooting: *Meringue - If you are finding the meringue continues to be grainy and the sugar doesn’t dissolve, this could be due to not measuring the eggs by weight. All eggs are slightly different in weight (approx 30g of white is standard) and if you have slightly less egg white than called for because you measured in ‘eggs’ rather than grams, you will find it might not fully dissolve. Simply add in slightly more egg whites and continue heating until you get all the sugar dissolved.