Heat oven to 200°C/180°C fan/gas 6. Butter and line a 23cm square tin with greaseproof paper.
Beat the butter and sugar with an electric whisk until light and fluffy. Add the eggs one at a time and beat well until combined. Add in the flour, milk and a pinch of salt and stir until combined. Add in a squirt of orange food colouring, a little at a time until you have a bright orange colour. Pour the mix into the tin and spread into an even layer. Bake for 20 – 25 mins until it’s golden and a skewer inserted comes out clean and leave to cool.
Trim each side so they’re straight. Cut the sponge into neat 3cm squares.
To make the chocolate coating, add the melted butter, milk and cocoa powder into a large bowl and whisk until everything is combined and there are no lumps. Whisk in the icing sugar, being careful to keep it all in the bowl until you have a smooth mix. If it’s not smooth you can whiz it with a stick blender.
Put half the desiccated coconut into a large shallow bowl, you can top it up when it’s nearly empty, it just saves the whole mix getting covered in chocolate.