• Preheat the oven to 180°C/160°C fan/350°F/Gas Mark 4 and line a 20cm diameter spring-form tin with baking parchment.
• Melt the chocolate and butter in a large heatproof bowl sitting over a saucepan of barely simmering water. Remove the bowl from the heat and mix in the sugar, vanilla extract, espresso powder, rum and ground almonds. Stir through the egg yolks, one at a time, mixing after each addition, until you have a thick batter.
• Put the egg whites in a standing food mixer (or use an electric hand-held mixer in a bowl) and whisk the egg whites until stiff peaks form.
• Loosen the chocolate mixture with a spoonful of the whites then gently fold through the rest of the egg whites until just combined.
• Pour two-thirds of the chocolate mixture into the prepared cake tin. Using a spoon, pour over the caramel sauce in an even layer, then cover with the remaining batter and place the tin in the oven to bake for about 35 minutes until it is firm but with a slight wobble.
• Remove the cake from the oven and allow it to sit on a wire rack to cool in its tin.
• Carefully remove the mud pie from the tin and transfer it to a cake stand with a lip to catch the caramel as it oozes out while still a little warm.
• Sprinkle the peanut brittle over the top and serve in generous slices.

Peanut Brittle

• Line a high sided baking tray with parchment paper.
• Combine the sugar with 120ml of water in a heavy-based saucepan over a medium-high heat. Once boiling, reduce the heat slightly and allow the mixture to simmer steadily for about 15 minutes, without stirring, until a golden caramel forms.
• Swirl the pan to encourage the sugar to caramelise. Remove the pan from the heat and stir through the peanuts. Spread the mixture on the prepared baking tray and allow to set for 30 minutes.
• Break up the brittle into small pieces.

Cheat's Salted Caramel Sauce

• Combine the sugar with 50ml of water in a heavy-based saucepan over a medium-high heat. Once boiling, reduce the heat slightly and allow the mixture to simmer steadily for about 15 minutes, without stirring, until a golden caramel forms.
• Remove the pan from the heat and mix in the cream and salt. Don’t panic when it bubbles and spits, return the pan to a low heat and the sugar crystals will re-melt.
• Add the butter and combine to form a smooth caramel sauce.