Line a 12-section bun tin with paper or foil cake cases. Grate the squash into a bowl and add all the remaining cake ingredients. Beat with a hand-held electric whisk for about a minute until light and creamy. Divide the cake mixture between the paper or foil cases.
Bake in a preheated oven, 180°C (350°F), Gas Mark 4, for 25–30 minutes or until just firm to the touch. Transfer to a wire rack to cool.
Roll out the orange and white icing on a work surface lightly dusted with icing sugar and cut out small star shapes, either by hand or using a cutter. Push a wooden cocktail stick into each and place on a sheet of greaseproof paper to harden for at least an hour.
Beat the fondant icing sugar in a bowl with 2 tablespoons orange juice, adding a little extra juice if necessary to give a thick but spreadable consistency. Spoon over the cakes, spreading to the edges. Take a teaspoon of the orange curd and pour it, in a loose spiral, over each cake. Push an icing star down into each cake. Just before serving, position the sparklers on the cakes and light.