Preheat the oven to <temperature>175<unit>°C</unit></temperature>

Line the bottom of a round, <quantity>20<unit>cm</unit></quantity> springform cake pan with parchment paper

Add <quantity>70<unit>g</unit></quantity> of unsalted butter and <quantity>70<unit>g</unit></quantity> of 50% chocolate to a medium saucepan and melt them over low heat. Let it cool down

Add <quantity>150<unit>g</unit></quantity> of all-purpose flour and <quantity>100<unit>g</unit></quantity> of white sugar to a bowl

Add <quantity>50<unit>g</unit></quantity> of cocoa powder and <quantity>1<unit>tsp</unit></quantity> of baking powder. Mix thoroughly

Crack <quantity>2</quantity> eggs-one at a time- into the cooled chocolate mixture and mix to combine

Gradually add <quantity>250<unit>ml</unit></quantity> of milk. Stir continuously

Add the dry mixture to the chocolate mix in 3 parts. Mix until you get a homogeneous batter

Pour the batter into the cake pan and bake it at <temperature>175<unit>°C</unit></temperature> for 45 m until it is fully cooked

While cake is baking, Add <quantity>30<unit>g</unit></quantity> of butter and <quantity>200<unit>g</unit></quantity> of chocolate 50% to a bowl

Melt them over a warm water bath, making sure the bowl doesn't touch the water. Remove from the heat

Add <quantity>70<unit>g</unit></quantity> of sour cream and <quantity>3<unit>g</unit></quantity> of salt. Mix until combined. Reserve in the refrigerator until the cake has cooled down

Pour and spread the glaze over the cake. Grate hazelnuts to taste. The chocolate cake with sour cream glaze is ready

Enjoy it with a good cup of tea!