Preheat the oven to 180 C / Gas 4. Line a 12 hole muffin tin with paper cases.
In a mixing bowl, beat the caster sugar and margarine with the rum extract and pink food colouring until creamy. In a separate bowl, lightly whisk together the eggs. Bit by bit add the beaten egg and sift in the flour into the butter-sugar mixture, mixing after each addition. The mixture should be ‘just drop off the spoon’ consistency.
Stir through the diced strawberries and fruit flakes. Spoon evenly into the prepared paper cases, pushing a raspberry into the centre of each one.
Bake for 20 to 25 minutes in the preheated oven until risen and golden, or until a skewer inserted into the centre comes out clean. Remove from the oven and cool completely on a cooling rack, about 1 hour.
For the strawberry and raspberry puree filling:
Meanwhile, make the puree by placing the strawberries, raspberries, icing sugar and cornflour into a saucepan over a low heat. Once the sugar has melted increase the heat slightly to bring the berries to a simmer. Continue to simmer until the mixture has thickened slightly. Use a masher to squash the berries (alternately blitz them in a food processor beforehand). Press the mixture through a sieve using the back of a spoon to get the most out of the berry pulp. Discard the pulp and set your fresh puree aside to cool.
Once cooled, pipe the puree into the centre of each cupcake, leaving at least 2 tablespoons for use in the buttercream.
For the buttercream icing:
Cream the butter and a dash of milk together. Add the reserved 2 tablespoons berry puree and food colouring, if using, and gradually sift in the icing sugar whisking well after each addition (I always find an electric mixer does the best job here). Once all of the ingredients are well combined, the icing should be smooth and spreadable. Due to the addition of the puree, the icing could curdle; if this happens keep adding icing sugar and beating it into the icing well until the curdling disappears. Spread or pipe icing onto the cupcakes.
For the decoration:
Decorate as desired with the berries, mint leaves and optional freeze-dried strawberries and glitter. If you’re feeling extra crazy, stick a straw in each cupcake to mimic the cocktail get-up. Now pretend you’re in an exotic beach-front setting, watching the sun go down over the glistening sea.
You can use 1 teaspoon liquid pink food colouring or 1/2 teaspoon colouring paste.
I always like to use real ingredients not colourings or flavours so I replaced the pink colouring in the buttercream with freeze dried strawberry powder from ebay. The flavour was amaaaaaazing. There is no moisture in the powder so you can just add it in, no need to rebalance your recipe as you do when you add wet ingredients. - 15 Nov 2015