Heat oven to 190°C/fan 170°C/gas 5. Butter two 20cm sandwich tins and line with non-stick baking paper.
In a large bowl, beat all ingredients for the cake together until you have a smooth, soft batter.
Divide the mixture between the tins, then bake for about 20 mins until golden. Remove from tins onto a cooling rack and set aside.
Add the juice of 1 orange, caster sugar and the sprigs of rosemary to a pan and bring to boil. Strain the syrup over the cooling sponges leaving 1 tbsp to add to the buttercream, then leave to cool completely. Keep the candied rosemary to decorate later.
To make the buttercream filling, beat the butter until pale and creamy, and then gradually beat in the icing sugar. Add the remaining tbsp of syrup and 1- 2 tbsp of milk depending on the thickness.
Completed steps (click to remove last step)
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