I love a good rhubarb cake but it’s so difficult to find a good one. You need to use good rhubarb, otherwise it doesn’t taste of much, you’ll have to make sure that its not too wet so your cake doesn’t just fall apart and I’ve worked on this recipe for soooo long just to get it right. And now I think I’ve created a very tasty rhubarb crumble cake recipe that I want to share with you.
- 300g Rhubarb (frozen, fresh or tinned and drained but keep the syrup)
- 2 tbsp Caster Sugar
- 2 tbsp Water
- 75g Cold, Unsalted Butter
- 50g Caster Sugar
- 25g Demerera Sugar
- 50g Plain Flour
- 50g Old Fashioned Oats
- 200g Plain Flour
- 50g Cornflour
- 1tsp Baking Powder
- Pinch of Salt
- 250g Soft Butter
- 250g Caster Sugar
- 5 Eggs, medium, seperated
- 1 tsp Vanilla Extract
- 250ml Rhubarb Syrup (add milk to make up 250ml if you don’t have enough syrup)
- 35g Caster Sugar
- 35g Cornflour
- 250g Butter
To begin with preheat the oven to 180 degree C and prepare an oven safe tray with a long strip of kitchen foil.
If you’re using fresh rhubarb, take the ends off and cut it in 2cm thick slices. If you’re using frozen rhubarb, defrost it first and catch all the juices that come out of the rhubarb in the process. Place the rhubarb on your prepared tinfoil, add the sugar and water stir everything around using a spoon until the rhubarb is completely coated. Then lay the pieces out flat with as few as possible overlapping and fold the kitchen foil over and close the “parcel” up on the top and the sides so that the rhubarb can’t burn. Bake the rhubarb for 25 minutes. Then carefully open the foil “parcel”, check if the rhubarb is nice and soft. Place a sieve over a bowl and carefully dip the contents of the kitchen foil into the sieve so that the syrup can drain off (don’t throw it away, we’ll need it later). There’s no need to use a spatula to push the liquid out, just let it sit for a few minutes.
Turn the oven temperature down to 170 degree C.
To prepare the crumble, put cold butter, sugars, flour and oats in a large bowl and rub them into each other using your fingers until they’ve reached a nice crumbly, clumpy texture and there are no more dry ingredients left in the bottom of the bowl. Put the crumble into the fridge to cool down.
For the sponge, grease and flour a 20cm spring form tin.
Put the egg whites into a large mixing bowl and start whipping them using a stand or hand mixer. Add the salt after a few seconds. This will help to break the structures in the egg whites up and make it easier to get them stiff. When they’re nice and fluffy add about 50g of the caster sugar and mix furter until it’s well incorporated and they’re slightly glossy. This will make it easier to mix the egg whites into the rest of the batter later.
In another mixing bowl cream butter and sugar together until they’re nice and fluffy and light in colour. Scrape the bowl down and add the vanilla extract, along with the egg yolks. You want to add them in 2-3 stages, mixing very well in between. Scrape the bowl down again. Combine flour and baking powder, add them to the batter and mix until they’re well incorporated. Combine cornflour and the baked/tinned rhubarb. This will contain any excess moisture and stop the rhubarb bits from sinking to the bottom of the cake when its baking. Add a quarter of the whipped egg whites and the rhubarb covered in cornflour and mix them in using the hand or stand mixer to loosen the batter up. Then add the rest of the egg whites and fold them in carefully using a spatula. Fill the batter into the prepared baking tin and place it in the lower half of the oven for 20 minutes.
After 20 minutes carefully remove the cake from the oven (don’t bang it on a surface as this will knock air bubbles out of the batter). Take the crumble and carefully scatter them over the top of the cake. Put the cake back into the oven for another 40-45 minutes. Take it out when you can put a skewer in the middle and it comes out clean. Let it cool down completely.
For the buttercream we need to first prepare the rhubarb custard. Put 200 ml of the rhubarb syrup we caught earlier (if you don’t have enough fill the 250ml up with milk) in a saucepan and slowly bring it to a boil. Combine the remaining 50ml with caster sugar and cornflour. When the syrup in the pan starts boiling take it off the heat and stir in the cornflour mixture. Now put it back on the heat and whilst whisking at all times let it cook for a minute until it’s nice and thick. Pour it into a bowl and cover the surface of the rhubarb custard with cling film. Let it cool down completely.
Whip the soft butter until it’s light in colour and fluffy in texture. Strain the cooled down custard through a sieve (it’s very thick so it will be a bit harder) with a wooden spoon or a spatula. While still whipping the butter, add the strained custard, one spoonful at a time. Scrape the bowl down and mix for another few seconds.
Take the cake out of the tin and cut it in half using a cake leveller or bread knife. Place the bottom half on a cake plate or stand. Add the buttercream and spread it to the edges of the cake using an offset pallet knife or spatula, then add the top layer (careful with the crumble, it crumbles off easily). I recommend cutting the cake carefully with a bread knife so that the cream doesn’t come out when you’re trying to get through the hard crumble layer.