A light genoise soaked with a vanilla milk syrup, filled with rhubarb jam and vanilla pastry cream, then covered in a mascarpone whipped cream
Nutrition: per serving (10)
To make the jam, put the rhubarb and lemon juice into a large pan, and cook over a medium heat until the rhubarb starts to soften. Add the sugar and cook for a couple of minutes or until the sugar is no longer visible and the rhubarb is very juicy. Turn up the heat to high and cook for 10 mins, stirring occasionally, or until the jam reaches the setting point of 104C (see tip, right). Pour the jam into a sterilised jar – it will keep chilled for a month.
To make the pastry cream, put the milk, vanilla and half of the sugar in a large pan over a medium-high heat, and bring to a boil. Meanwhile, put the remaining sugar, cornflour, yolks and a pinch of fine sea salt in a large bowl and whisk until smooth. Once the milk is bubbling, pour it into the yolk mixture, whisking to combine. Pour the custard back into the pan and cook, whisking constantly, until the pastry cream is bubbling and thick. Continue cooking for another minute to ensure the cornflour is fully cooked. Scrape the pastry cream into a bowl and whisk through the butter until the custard is smooth. Cover and refrigerate until needed – this can be prepared a day in advance.
Heat the oven to 180C/160C fan/gas 4 and lightly butter an 8cm-deep 20cm round cake tin and line the base and sides with baking paper, making sure it reaches 2-3cm above the top of the pan as the cake can rise significantly.
To make the genoise, put the eggs and sugar into a large heatproof bowl over a pan of simmering water and whisk gently until the mixture reaches around 40C. If you don’t have an instant-read thermometer, you can use your fingers to test – the mixture should feel warm with no grains of sugar remaining. Remove the bowl from the heat and mix with an electric whisk on high speed for 7-8 mins until the mixture has tripled in volume. Reduce the speed to medium and mix for another 2 mins. Lastly, reduce the speed to low and whisk for a final 2 mins. This method of whisking ensures maximum aeration but also refines the foam to ensure no large bubbles, resulting in the best texture for the cake.
Melt the butter with the milk in a small pan over a low heat, then set aside. Sift the flour and cornflour over the egg mixture in three additions, folding lightly to avoid knocking out too much air. Add a large spoonful of the batter to the melted butter mixture and mix until emulsified. Scrape this back into the main batter and fold to combine. Pour this batter into the prepared tin and firmly tap on a worksurface to knock out any large air pockets. Bake for 30 mins or until the cake springs back from a light touch. Remove and drop onto the worksurface from a few inches (this prevents the cake from shrinking). Cool for 5 mins before inverting onto a wire rack to cool completely. Mix together the milk soaking syrup ingredients in a jug.
To assemble, use a serrated knife to cut the cake into three even layers. Remove the pastry cream from the fridge and beat until smooth. Put one of the cake layers onto a large plate and brush liberally with the milk soaking syrup. Top with half of the pastry cream and spread to the edges. Top with thin layer of jam and repeat with the second layer of cake, reserving a little of the jam for the top. Brush the cut side of the final cake layer with the milk soaking syrup and then put, cut side down, on top.
Whisk the mascarpone, sugar and vanilla in a large bowl until smooth. Pour in the whipping cream and whisk until the mixture holds soft peaks. Use most of it to coat the outside of the cake. Add a little of the cream mixture to a piping bag fitted with a large star tip and pipe small rounds around the edge of the cake. Dip a small measuring spoon in hot water and press the mounds of cream to make small wells, then spoon a little jam into each well. The cake will keep chilled for two days.
