Prepare a rich, well-colored caramel and line each 10 cm charlotte mold with it.
Arrange the peeled, cored, and quartered apples (reserving 3 for garnish) on a baking sheet with a little butter and 400 g caster sugar. Bake until soft and melting, then transfer to a work surface and coarsely crush with a knife.
Whip the egg whites to very stiff peaks, then gently fold into the warm apple mixture using a spatula.
Fill the prepared molds to 1 cm below the edge.
Bake in a 200°C oven using a bain-marie for 20-25 minutes. Cool completely and chill in the refrigerator.
For the garnish, peel and core the reserved 3 apples, slice into thin strips, and sauté in butter and sugar until caramelized.
Unmold the soufflés onto chilled plates 30 minutes before serving.
Drizzle with extra caramel, sprinkle with chopped hazelnuts, and top with caramelized apple slices.
*Starking or Granny Smith apples recommended.
