To toast hazelnuts, spread them on a baking sheet and bake at 350 degrees F (175 degrees C) for 8-10 minutes, or until fragrant and lightly browned. Let cool slightly, then rub the skins off with a clean kitchen towel. For easier cutting, chill the blondies in the refrigerator for 30 minutes before slicing. Store leftover blondies in an airtight container at room temperature for up to 3 days.