Rhubarb custard cake

The combination of rhubarb and custard is simply irresistible! This moist rhubarb layer cake has a subtle orange flavour and is filled with custard cream and roasted rhubarb. I’ve skipped the usual sponge cake here because I’ve been making so many lately, but there’s nothing to stop you from using one for this cake instead. The cake layers are not particularly thick, but I think they’re just right – there’s plenty of custard and rhubarb to enjoy :). Thanks to the gelatine, the chilled cake will hold up well at room temperature, even outdoors at a family picnic; however, you can leave the gelatine out if you prefer. An absolutely fabulous cake, perfect for the weekend!

Ingredients for the cake:

• 115 g butter
• 100 g caster sugar
• 2 large eggs
• 140 g plain flour
• 40 g potato starch
• 1 tsp baking powder
• 100 g sour cream
• finely grated zest of 1 orange

All ingredients should be at room temperature.

Place the butter and sugar in the bowl of a stand mixer. Beat until light and fluffy. Add the eggs one at a time, beating well after each addition until fully incorporated. Add the orange zest and beat to combine (the mixture may look curdled at this stage, but this will not affect the finished cake). Sift the flour, baking powder and potato starch directly into the bowl with the butter and egg mixture, then add the sour cream. Fold gently with a spatula just until combined, no longer.

Line the base of a 22–23 cm round cake tin with baking paper. Transfer the batter to the tin and level the surface.

Bake at 170°C for about 35–40 minutes, or until a skewer inserted into the centre comes out clean. Remove from the oven and leave to cool.

Cut the cake horizontally into 2 layers.

Ingredients for the custard cream:

• 1 packet of unsweetened vanilla custard powder (a packet for 500 ml milk)
• 250 ml milk
• 3 tbsp sugar
• 250 g mascarpone, chilled
• 2 tsp powdered gelatine + 40 ml cold water

Cook the custard with 3 tbsp sugar according to the instructions on the packet, using 250 ml milk instead of 500 ml. Bring to the boil, cook briefly until thickened, then remove from the heat. Transfer to a bowl and cover with cling film, pressing it directly onto the surface of the custard to prevent a skin from forming. Leave to cool, then chill in the fridge.

Sprinkle the powdered gelatine over 40 ml cold water and leave for 10 minutes to bloom. Place over low heat and warm, stirring, until the gelatine has completely dissolved; alternatively, heat it briefly in the microwave. Do not allow it to boil, as this will destroy its setting properties. Remove from the heat and leave to cool slightly, but it should remain liquid.

Place the chilled mascarpone in the bowl of a stand mixer and briefly beat using the whisk attachment. Add the cold custard in three batches, continuing to beat. The custard will be thick and lumpy at first, but as it is beaten with the mascarpone it will transform into a smooth custard cream (be patient!).

Mix the cooled gelatine with a little of the custard cream, for example 1–2 tbsp, to avoid a sudden temperature change and prevent gelatine lumps from forming in the cream. Add the tempered gelatine mixture to the remaining custard cream and beat until combined.

Ingredients for the roasted rhubarb:

• 500 g rhubarb, cut into 2 cm pieces (do not peel)
• 50 g sugar

Mix all the ingredients and place in an ovenproof dish or on a baking tray lined with baking paper.

Bake at 180°C for about 15–20 minutes, until the rhubarb has softened slightly (it must not fall apart; it should retain its shape). Remove from the oven and leave to cool. Drain off any syrup that has collected (see the end of the recipe).

Assembly:

Place the first cake layer on a serving plate. Arrange the roasted rhubarb pieces on top, side by side. Spread the custard cream over the rhubarb, then place the second cake layer on top. Chill.

Before serving, dust the rhubarb cake with icing sugar or drizzle with rhubarb icing. To make the icing, mix the reserved rhubarb syrup with icing sugar, rubbing them together with the back of a spoon until you reach the desired icing consistency (I didn’t have enough syrup, so I skipped this step).

Enjoy!