Pre-heat your oven to 160C Fan/350F/Gas Mark 4 and grease two 6-hole donut tins with butter or baking spread
Mix together the caster sugar, milk, vegetable oil and eggs in a bowl with a whisk
Add the self raising flour and cocoa powder and whisk in until smooth
Divide the batter between the tins. You can put the batter into a piping bag or a jug to make it a bit neater to dispense into the trays, but you can do it with a spoon too
Bake them for 12 minutes, then remove them from the tin (I use a spoon to gently prise them out) and leave to cool on a cooling rack
Melt the dark chocolate and white chocolate in separate bowls. You can melt it in the microwave, make sure to use a microwave safe bowl. Heat the chocolate for 30 seconds, stir it, then heat in 10 second bursts, stirring in between
Set the donuts onto a rack with a baking tray underneath to catch any drips of chocolate
Dip the top half of the donuts in the dark chocolate and place back on the rack
Put the white chocolate in a small piping bag and cut a very small amount off the end, pipe three thin circles on the donuts on top of the dark chocolate, then use a cocktail stick to drag through the lines to create the spider web effect
Leave to set, or put them in the fridge to set the chocolate faster
Store leftover in an airtight container and eat within 3 days