For the cupcakes
Heat the oven to 180°C (160° fan) 350°F gas 4.
Place 12 cupcake cases in a bun tin.
Mix the pureed lychees with the milk and vanilla extract.
Cream the butter and sugar until soft and light.
Add the egg and egg whites and mix until blended.
Sift in the flour, baking powder and salt and stir until combined.
Add the lychee and milk mixture and mix until just combined.
Spoon the mixture into the paper cases and bake for 20-25 minutes until the tops are lightly golden and springy to the touch.
Leave to cool in the tins for 10 minutes, then place on a wire rack to cool completely.

For the buttercream
Beat the butter until very soft and creamy.
Gradually beat in the icing sugar and milk, followed by the rose water and colouring and beat until smooth.
Pipe or spoon the frosting onto the cupcakes and top each with a rose petal.