01 - Preheat oven to 350°F. Grease and line an 8-inch round cake pan with parchment paper.
02 - In a large bowl, whisk together hazelnut flour, sugar, baking powder, and salt.
03 - In a separate bowl, whisk egg yolks, milk, olive oil, and vanilla extract until smooth.
04 - Add wet ingredients to dry and stir until just combined.
05 - Beat egg whites in a clean bowl until stiff peaks form, then gently fold into the batter.
06 - Pour batter into prepared pan, smooth the surface, and bake for 30 to 35 minutes until a toothpick inserted in the center comes out clean.
07 - Let cake cool in the pan for 10 minutes before transferring to a wire rack to cool completely.
08 - Gently heat chocolate-hazelnut spread with cream in a saucepan over low heat, stirring until smooth and pourable.
09 - Drizzle warm sauce over cooled cake. Dust with powdered sugar and optionally top with chopped hazelnuts.