Orange Sponge Cake with Mandarin Buttercream

Ingredients

• ORANGE SPONGE
• 4 eggs, separated
• 1 pinch salt
• 10 g vanilla sugar
• 130 g sugar
• Finely grated zest of 1 orange
• 90 g orange juice
• 30 ml vegetable oil
• 160 g flour
• 30 g cornflour
• 7 g baking powder
• ORANGE BUTTERCREAM
• Finely grated zest of 2 oranges
• 250 ml orange juice, from approximately 3 oranges
• 120 g sugar
• 35 g cornflour
• 200 ml cold water
• 250 g butter, softened
• 1 tin mandarins, thoroughly drained

Method

1. Preheat the oven to 170°C (338°F).
2. Grease and line a 20 cm cake tin.
3. Separate the eggs.
4. Whisk the egg yolks with the vanilla sugar and sugar until pale and thick.
5. Add the orange juice, vegetable oil and orange zest.
6. Sift together the flour, cornflour and baking powder.
7. Fold the dry ingredients into the egg-yolk mixture.
8. Whisk the egg whites with the salt until firm peaks form.
9. Fold the egg whites carefully into the batter.
10. Transfer the batter to the prepared tin.
11. Bake for approximately 35–40 minutes, until risen and a skewer inserted into the centre comes out clean.
12. Leave the sponge to cool completely.
13. For the orange custard, combine the orange zest, orange juice, sugar, cornflour and cold water in a saucepan.
14. Cook over medium heat, whisking constantly, until very thick.
15. Cover the surface and leave the custard to cool completely.
16. Beat the softened butter until pale and fluffy.
17. Add the cooled orange custard gradually, beating well after each addition.
18. Fold the well-drained mandarins into part of the cream or use them between the cake layers.
19. Slice the cooled sponge into layers.
20. Fill and cover the cake with the orange buttercream.
21. Refrigerate for at least 30 minutes before serving.