Line a casserole dish of about 20x20 cm/ 8x8 inch with plastic foil.
Roast the hazelnuts in a pan without any fat, for a few minutes or until fragrant. Stand by and shake the pan very often to avoid them burning. Immediately remove the nuts from the pan and let cool.
Rub the nuts between your palms to remove some of their brown skin. You don't have to get it all away, just as much as you manage.
Without a food processor:
Chop the roasted hazelnuts roughly using a chef's knife. Place in a bowl.
Crush the cornflakes roughly with your hands. Add to the hazelnuts.
Crush the hard candy using a meat mallet or a heavy, sturdy pan. Set aside separately from the rest.
Melt the chocolate au bain-marie. Once it is fully melted, add the salt and the oil. Pour over the hazelnuts and the cornflakes. Mix very well.
Pour the mixture into the prepared pan, sprinkle with the crushed candy.
Thermomix or another good food processor that can manage crushing the hard candy:
Chop the roasted hazelnuts for 6 seconds on level 6. Transfer to a bowl. Roughly crush the cornflakes for 3 seconds on level 5. Add to the bowl with the hazelnuts.
Crush the hard candy for 3 seconds on level 5. Transfer to a separate bowl.
Chop the chocolate pieces for 6 seconds on level 5. Add the salt and the oil and melt for5 minutes/50 degrees Celsius/ level 2. Add to the bowl with the hazelnuts and cornflakes and mix well.
Pour the mixture into the prepared pan and sprinkle evenly with the crushed caramel candy.
Let set: Place the dish in the fridge for a couple of hours until the chocolate is set again. Chop into smallish squares. I prefer to eat it cold, straight from the refrigerator. It keeps well in the fridge.