Mimosa cake

Ingredients

• 2¼ cups (335g) plain flour
• ½ cup (75g) corn flour
• 1½ cups (330g) caster sugar
• 1 tbsp baking powder
• 1 tbsp finely grated orange rind
• ½ tsp fine sea salt
• 150g unsalted butter, softened and chopped
• ¾ cup (180ml) vegetable oil
• 2 eggs, room temperature
• 1 cup (250ml) Champagne, at room temperature, plus extra to brush
• 1 cup (250g) sour cream, at room temperature
• 2 tsp vanilla extract
• Dried orange slices, to decorate
• Champagne icing
• 750g cream cheese, chopped and softened
• 150g unsalted butter, chopped and softened
• 3 cups (480g) icing sugar mixture, sifted
• 2 tbsp Champagne