Directions

1. Heat oven to 190C/170C fan/gas 5. Line a baking sheet with baking parchment. Using an electric whisk, beat the butter and sugar together in a large mixing bowl until pale and fluffy. Gradually beat in the egg and vanilla extract.
2. Stir in the flour, then knead the mixture briefly to make a dough. Divide the dough in half. One half can now be frozen or chilled to make another batch of biscuits. On a floured work surface, roll out the remaining dough to the thickness of a PS1 coin. Using plain round biscuit cutters, cut out the following size biscuits: 1 x 8cm, 2x7cm, 4x6cm, 2x5cm and 1x3.5cm.
3. Carefully transfer the biscuits to the prepared baking sheet and bake for 10-12 mins until pale golden brown. Leave them on the baking sheet for 5 mins, then transfer to a wire rack to cool completely.
4. Mix the icing sugar with 2-3 tbsp water to make a smooth, spreadable icing - it shouldn't be too runny. Spoon 1 tsp of the icing into a small bowl and mix enough yellow food colouring to make it bright yellow, then use to cover the largest biscuit and set aside to dry.
5. Spoon 2 tsp of the white icing into another small bowl and mix in enough blue food colouring to make it a bright, light blue. Use a little of this icing to cover a 6cm biscuit to make Uranus. Set aside to dry.
6. Add a little more blue colour to the blue icing and use a little to cover another 6cm biscuit, to make the water on the Earth. Set aside to dry. Add a little more colour to the blue icing and cover another 6cm biscuit. Using a cocktail stick, swirl a little extra blue food colour and white icing onto this iced biscuit to make Neptune. Set aside to dry. Add a little more blue and a tiny bit of black food colouring to the blue icing and spread it over the 3.5 cm biscuit to make Pluto. Set aside to dry.
7. For Mercury, spoon 1 tbsp of the white icing into another bowl and add enough of the caramel flavouring to make a beige colour. Spread a little of it over a 5cm biscuit. Using a cocktail stick, swirl a little extra caramel flavouring into the icing on the biscuit. Set aside to dry.
8. Spread a little of the beige icing over a 7cm biscuit. Using a cocktail stick, swirl in a little red food colouring and white icing to make the patterns of Jupiter. Set aside to dry.
9. For Saturn, add a little yellow food colouring to the beige icing and spread it over the other 7cm biscuit, leaving a 1cm border around the edge. Use a cocktail stick to swirl a little yellow food colouring into the icing and set aside to dry.
10. For Venus, add a little orange food colouring to the beige icing and spread some over the remaining 6cm biscuit. Using a cocktail stick, swirl in a little orange. Set aside to dry.
11. To finish Earth, spoon 1tsp white icing into another small bowl and add enough green food colouring to make it bright green. Blob a little of the green icing over parts of the blue icing.
12. For Mars, spoon 1tsp white icing into a small bowl and add enough red food colouring to make it bright red. Spread the red icing over a 5cm biscuit. Using a cocktail stick, swirl a little red food colouring into the icing. Set aside to dry.
13. Fit a plain nozzle to a piping bag and add the remaining white icing. Pipe 2 stripes around the middle of the Saturn biscuit to give it its rings. If you like, you can sprinkle the Mercury and Venus biscuits with a little edible gold glitter to make them sparkle.