Place 2 inches of boiling water into a medium sized saucepan and bring to a low simmer.
Put the orange juice, sugar and butter in a heat proof bowl and suspend over the simmering water. Stir until melted.
Add the beaten eggs, and stir constantly with a wooden spoon for 20-25 minutes until the mixture is thickened and smooth. The mixture will coat the back of the spoon when it is ready, and a finger, drawn along the back, will leave a line.
Strain to remove any bits of cooked egg white, and pour into a sterilized bottle.
to make the butterfly cakes
Preheat oven to 200 C. Line a muffin tin with 10-12 cupcake cases, depending on their size.
Cream the butter and sugar together until light and fluffy.
Beat in the eggs and vanilla, and sift over the flour.
Combine well, adding 1-2 tbsp of orange juice to reach a soft, dropping consistency.
Spoon the batter into the prepared baking cases and bake for 15-20 minutes, until golden and springy on top.
Leave to cool before carefully slicing the tops of the cakes off. Cut each top in half to form the butterfly wings.
Using a small spoon, scoop about 1 tsp out of the centre of each cake (scoff these while assembling!).
To prepare the frosting, beat the icing sugar, butter, orange curd and enough milk together to form a pipable consistency.
Spoon 1 tsp of orange curd into the centre of each cake, and top with a swirl of orange butter cream frosting.
Push the two halves of the cupcake top into the frosting to form butterfly wings, and lightly dust with powdered sugar before serving.
Mum of three, daydream adventurer, OU Life Sciences graduate, occasional crafter, ex-pat Canadian & quite possibly Britain's most northerly food blogger.