4tbspsimple syrupa solution of water and sugar in equal parts
2dropsrose water
For the Mascarpone Cream
500g/2 cupsmascarponechilled from fridge
250ml/1 cupdouble/whipping cream
100g/1/2 cupicing sugar
2tspvanilla
2-3dropsrose water or less depending on the strength of rose water
For decoration
lemon thyme sprigs
organic pink flowers
dried rose petals
Instructions
For the Rhubarb Curd
*Prepare the rhubarb curd at least a day before assembling the cake. Wash and cut rhubarb stalks in 2" sections, put them in the bowl of a food processor and process until then turn into a pulp. Push it through a fine sieve with a spoon to extract all the juice, then discard the pulp. You should get about 300 ml/ 1¼ cup of rhubarb juice.
In a food processor or blender mix eggs, sugar and cornflour/corn starch until you have a homogenous mixture with no lumps remaining. Alternatively you can do this step by hand using a bowl and a whisk.
In a saucepan combine 1 cup of rhubarb juice, egg, sugar and corn starch mixture and cubed butter, set the pan over low heat and star cooking it while stirring with a whisk the entire time until butter melts and the curd thickens. Do not turn the heat up to speed up the process or the eggs will turn into scrambled eggs and the curd go lumpy!
Take off the heat when the curd is the consistency of thick sour cream. You may push it through a fine sieve again to ensure there are no lumps and the curd is silky smooth. Add the remaining rhubarb juice to increase the tart flavour of the rhubarb and a drop of pink food colouring if desired as the curd loses its colour when cooks!
Chill in the fridge for at least 3 hours or overnight. The rhubarb curd will thicken when chilled.
For the Cake
Preheat the oven to 350F/180C.
Grease 3 8" cake pans and line them with parchment paper. (Don't be tempted to skip this stage, the sponge is very delicate, so it's important to use parchment paper for easy removal.)
Crack 5 eggs at room temperature to a bowl of a stand mixer and add sugar and vanilla been seeds, beat at high speed for 5 minutes until the mixture is pale and triples in volume.
Fold in flour through a sifter in 3 additions blending it in gently after each addition. Your goal is to keep the volume of the egg mixture so be very careful in this step of the process.
Divide your cake batter among 3 pans, I weigh mine to make sure they are exactly the same and bake for 25-30 minutes until cake tester or tooth pick comes out clean and the cakes have risen to the top of the pan. (I baked 2 layers and then 1 later).
Cool for 10 minutes and then run a knife around the edges of your pans to release the cakes and flip them over on a wire rack to cool completely.
(After your cakes have cooled you can individually wrap them in plastic wrap for later use. You can bake you sponge layers up to 2 days ahead.)
For the Syrup
In a measuring cup mix together simple syrup, elderflower liqueur for beautiful floral notes and 2-3 drops of rose water, the amount of which largely depends on the strength of it. Each brand is different, so it's important to taste and smell to determine the desired amount. Add with caution as it can smell like a perfume instead of a dessert if too much rose water is used.
For the Mascarpone Cream
In a bowl of a stand mixer whip well-chilled mascarpone for no longer than 30 seconds with a balloon attachment until light, add heavy/double cream, icing sugar, vanilla and rose water and whip for 1-2 minutes longer until it looks like thick whipped cream. If your mascarpone cream is too thick and hard to spread add a splash of heavy/double cream and whip for just a few seconds longer to loosen it.
Assemble the cake
Load ⅓ of mascarpone cream in a large piping bag with a plain round tip.
Pipe a border around the first drizzled with syrup layer, this will prevent rhubarb curd filling from spilling out, fill the space inside the border with rhubarb curd.
Top with the next layer and repeat the actions. Place the third layer on top and cover the entire cake with a thin layer of mascarpone cream also known as crumb coating. Place in the refrigerator for 30 minutes. When the crumb coat is firm frost the cake with the rest of the mascarpone cream.
Decorate the top with lemon thyme, small organic pink flowers and rose petals.