1. line a pan with parchment paper. 2. Place cornflakes in a large bag and crush them into small pieces. transfer the crushed cornflakes to a large bowl, and add the chopped pecans. 3. Place dark chocolate in a microwave-safe bowl. heat for 25 seconds at a time, stirring after each interval, until the chocolate is fully melted. 4. Add the melted chocolate, chocolate hazelnut spread, and salt to the bowl with the cornflakes, and mix until well combined. 5. Press the cornflake mixture into the prepared pan, smoothing the top gently. 6. Place the pan in the freezer for 10 minutes, or until fully set. 7. While the cornflake mixture is setting, prepare the chocolate ganache. place chocolate chips in a large bowl. 8. In a saucepan over medium heat, bring the cream just to a boil, then immediately pour it over the chocolate chips. whisk until smooth and combined. 9. Pour the chocolate ganache over the set cornflake mixture. 10. Refrigerate for at least 2 hours to allow the ganache to set. 11. Before serving, sprinkle flaky salt and roasted hazelnuts on top. 12. Cut into bars and serve.