1. Preheat the oven to 140 degrees Celsius (275 degrees Fahrenheit) Gas 1.
2. Leaving the skin on, cut the apple into thin slices using a mandoline or a sharp knife. Toss the slices in lemon juice to prevent them browning, then dust in a little cinnamon. Lay the slices out ﬂat on a baking sheet and place in the preheated oven for one to one and a half hours, until dried but still slightly soft. (This will make more dried apple than you need for decoration, but they will keep well and make a great healthy snack if stored in an airtight container.)
3. Place the sugar in a saucepan and heat gently over a low heat until melted. Do not stir, but swirl it to ensure that the sugar does not burn. Once the sugar has melted, carefully dip some of the baked apple slices into the caramel — only dipping them in halfway. (Use tongs and take extreme care as the sugar is very hot and can burn you.) Place the apple slices on a silicon mat or lined baking sheet and leave to dry.
4. Add the milk to the remaining caramelized sugar in the pan. Do not worry if the sugar solidiﬁes, as it will melt on heating. Simmer over low heat until the sugar dissolves. Add the chocolate and stir until melted. Remove from the heat and add the Apfelkorn, if using (do not return the mixture to the heat as it may curdle the milk). Pour the hot chocolate into two cups or heatproof glasses, top with a little whipped cream and drizzle with caramel sauce or dulce de leche. Place an apple slice on top of each cup. Serve at once.