For the fondants, finely grate 40g/1½oz of the chocolate.
Use half of the butter to grease three individual pudding moulds or ramekins. Sprinkle around the inside of each mould with the grated chocolate, shaking out any excess.
Place the remaining chocolate (including any excess shaken out from the moulds) and butter into a small heatproof bowl over a pan of barely simmering water and heat until melted, stirring occasionally. Alternatively, place into a microwaveable bowl and cook in the microwave on full for 2-3 minutes, stirring once. Do not overheat or the chocolate will 'seize', or turn solid. Scrape the chocolate mixture into a bigger bowl, then beat in the ground almonds, egg yolks and cornflour.
Whisk the egg whites in a separate clean bowl until they form stiff peaks when the whisk is removed. Gradually beat in the caster sugar until the mixture is smooth and glossy.
Fold the egg white mixture into the melted chocolate mixture. Divide half of the mixture among the three moulds, then top each with a chocolate truffle. Fill each mould up almost to the top with the remaining mixture, then smooth the tops with a palette knife and place into the fridge to chill for a few minutes.
Preheat the oven to 180C/350F/Gas 4.
Place the moulds onto a baking sheet and bake for 10-15 minutes, or until risen but still gooey in the middle.
Meanwhile, for the mint froth, heat the milk in a small saucepan until just boiling. Remove from the heat, add the crème de menthe and stir well. Using a hand blender, blend the mixture until frothy.
To serve, place the chocolate fondants onto plates and drizzle over the mint froth. Serve with the summer berries.