Preheat the oven to 180°C (350°F).
Line the bottom of an 8-inch (22 cm) springform pan with baking or parchment paper.
Lightly grease the sides of the pan with a neutral oil.
In a medium bowl, combine all your dry ingredients: plain or all-purpose flour, hazelnut meal, sifted cocoa powder, baking powder, baking soda, and salt. Set this mixture aside.
In a large mixing bowl, whisk the eggs and brown sugar together for 3 to 4 minutes, or until the mixture thickens, increases in volume, and becomes bubbly.
Next, whisk in the cooled melted butter, followed by the yogurt.
Gently fold in the pre-mixed dry ingredients (sifted if necessary) until everything is combined. Stop mixing as soon as there are no dry ingredients visible; the batter should be slightly thick.
Pour the cake batter into the prepared pan, spreading it evenly. If you like, add a generous sprinkle of roughly chopped hazelnuts and chocolate chunks on top.
Bake for 45 minutes, or until a toothpick inserted into the center of the cake comes out clean. Once done, transfer the cake pan to a cooling rack and let it cool completely before removing the cake from the pan.