Preheat the oven to 180°C (160°C for fan assisted ovens)/Gas Mark 4. Line 2 x 12-hole muffin trays with paper cupcake cases.
Make, bake and cool the cake mix as directed on the box for cupcakes using the oil, water and eggs.
To decorate, put the icing in a mixing bowl and beat in enough of the yellow food colouring paste or gel to give a striking sunflower yellow colour (see Tips). Spread a thin layer of icing over the cupcakes. Spoon half of the remaining icing into a piping bag fitted with a small star nozzle. Pipe 6 lines from the centre of each cupcake, out to the edge, making an evenly spaced, ‘spoke-like’ pattern on each. To create the petals, start in the centre and pipe a loop by going down 1 side of each spoke, turning at the edge of the cupcake and following the next spoke back into the centre. Repeat to create 6 loops, filling the piping bag with the remaining icing, as required.
Fill the centre of each cupcake with chocolate chips, pointed-side down. Serve immediately and store any leftover cupcakes in an airtight container in a cool place for 2-3 days.