Method Prep:15min › Extra time:2hr setting › Ready in:2hr15min
Break the dark chocolate into a heatproof bowl and place over a saucepan of barely simmering water to melt.
Meanwhile, line a baking tray with baking parchment. Once the chocolate has melted, scrape it out of the bowl on to the centre of the paper using a spatula. Carefully spread the chocolate to form a rectangle, about 18x23cm (7x9 in). Tap the tray lightly on the work surface to smooth and settle the chocolate and put in a cool place to set.
Melt the white chocolate in the same way. Remove the bowl from the water and mix in about 35 drops pink gel food colour to make a pretty pink shade.
Once the dark chocolate layer has set, scrape the pink chocolate out of the bowl on to the centre of the dark chocolate. Using a spatula, carefully spread the pink chocolate to almost cover the dark chocolate. Tap the tray lightly on the work surface to smooth and settle the chocolate.
Working quickly, before the pink chocolate sets, decorate the top with chocolate hearts, sugar hearts and hundreds and thousands, then put in a cool place to set firm.
Once the chocolate is firm, break into pieces and either serve and enjoy as they are or pack pieces into boxes or cellophane bags for gifting.