Separate the egg yolks from the whites into two bowls.
Soften the butter slightly in the microwave, let it cool, then mix it with the egg yolks and sugar until smooth.
Sift together the flour, cornstarch, and baking powder, then gradually add to the egg mixture, stirring well.
Roughly chop and toast the hazelnuts in a dry pan until golden and fragrant, then let them cool. Add the toasted hazelnuts and chocolate chips to the batter and mix well.
Whip the egg whites to stiff peaks, then gently fold them into the batter with downward motions to keep the mixture light.
Line a baking pan with parchment paper and pour in the batter.
Peel, core, and slice the pears, then arrange them on top of the batter. Sprinkle with raw cane sugar for a crunchy crust.
Bake in a preheated static oven at 350°F (180°C) for about 40 minutes. If the top browns too quickly, lower the temperature to 325°F (160°C).
Check doneness with a toothpick — if it comes out clean, the cake is ready.
Turn off the oven, leave the cake inside for 5-7 minutes, then crack the door open and let it rest for 10 minutes more.
Cool completely before serving. For even better flavor, make it a day ahead.