Rhubarb and Custard Cupcakes

These may look innocent enough, but they have a hidden centre of rhubarb curd under that vanilla flavoured icing.  The sponges are a little different too, they're made with custard powder in the batter to give that real rhubarb and custard taste of a British summer.
If you don't want to make the curd, you could use rhubarb jam instead, but I can assure you, it's well worth a try if you fancy a go at something different.

 Equipment -
Electric whisk
Sugar thermometer
12 hole muffin tin lined with paper cases

Ingredients -

Rhubarb curd -
600g rhubarb
4 large, free range eggs
200g butter, diced
4 tsp cornflour
175g caster sugar

Sponges -
100g custard powder
200g butter, softened
2 large, free range eggs
4 tbsp milk
140g caster sugar
100g SR flour, sifted

Icing -
170g caster sugar
120ml water
4 free range egg yolks
300g butter, very soft but not runny
1 tsp vanilla bean paste

Method -

Rhubarb curd -
You'll find the recipe here.

Sponges -
1. Heat oven to 180C, fan 160C, gas 4.
2. Beat the custard powder with the eggs, sugar, milk and a tablespoon of the flour, using an electric whisk.
3. Divide between the cake cases and bake for about 20 mins, until golden and springy to the touch.
4. Leave to cool completely.

Icing -
1. Put the sugar and water in a small pan and heat gently, without boiling until the sugar dissolves.
2. Boil until temperature reads 110C on a sugar thermometer (5 mins or so).  Don't let it caramelize.
3. Put the egg yolks in a large bowl and whisk briefly.
4. Pour the sugar syrup  into the egg yolks with the electric whisk running, in a slow, steady stream.
5. Keep whisking until mixture is pale, thick, mousse like and totally cold.
6. Gradually whisk in the butter, followed by the vanilla.

To assemble -
Use a cupcake corer or apple corer to remove a plug of sponge from the centre of each cake.  Fill almost to the top with the curd.  Cut the crust off the removed plug and replace it to cover the hole.  Ice as desired, I used a piping bag fitted with a star nozzle and some sugar crystals.  I thought I had some more exciting decorations in the cupboard but was sadly mistaken!