Preheat a water bath to 90°C

Break the chocolate into pieces, place in a vacuum bag and seal with a bar sealer. Cook in the water bath for 6 hours

When the chocolate is ready, warm the milk to around 50°C. Squeeze any excess liquid out of the gelatine and add to the milk, stirring to dissolve

Transfer the caramelised chocolate to a bowl and mix well until it forms a paste. Use a hand blender to gradually blend in the warm milk

Once all the milk has been added, chill the mixture for 20 minutes. Blend again, place in the fridge for another 20 minutes, then blend again

Whisk the double cream to very soft peaks and fold into the chocolate mixture using a whisk. Transfer to a plastic tub and chill overnight to set completely

Preheat the oven to 160°C/gas mark 3

To make the streusel crumb, sift the dry ingredients together into a small bowl. Rub in the butter and bring together into a rough dough

Spread onto a silicone baking mat and bake for 10–12 minutes until golden brown. Roughly break up with a fork then continue to cook for 2–3 minutes more. Allow to cool

In a non-stick frying pan, heat the butter until foaming. Add the apple slices and sprinkle over the sugar. Cook until well caramelised

To serve, dip a dessertspoon into warm water and use to create quenelles of the mousse. Garnish with the caramelised apple and sprinkle over some streusel crumb