Beat together all the cake ingredients in a bowl until smooth and creamy. Divide the mixture evenly between paper cupcake cases arranged in a 12-hole cupcake tray.
Bake in a preheated oven, 180°C (350°F), Gas Mark 4, for 20–25 minutes until risen and just firm to the touch. Transfer to a wire rack to cool.
Make the frosting. Beat the cream cheese in a bowl until softened and smooth. Add the butter and most of the elderflower cordial and beat until smooth and creamy. Add more cordial if the frosting will absorb it without losing its shape. Spread over the cupcakes and decorate with elderflower sprigs, if using.