Preheat your oven to 180 C / 350 F . Butter a 4 or 5 inch round pan (s) and dust with flour. Line the bottom with parchment if you have it.Whisk together the flour, salt , cocoa and baking powder in a small bowl.In another bowl , whisk together the egg, vanilla , milk and oil.Mix in the sugar for a minute or two.Add or sift in the dry ingredients. Whisk until smooth.Pour batter into prepared pan(s) and bake at 180 c / 350 F in the preheated oven for 22- 24 minutes if using a 5 inch pan , and around 25 minutes using a 4 inch pan. A toothpick inserted in the centre comes out clean.Cool in pan for 5 minutes , remove from pan and cool completely on wire rack.The Nutella Buttercream You'll need:IngredientsSteps

Beat the butter for several minutes until pale, light and fluffy.Add the salt and icing sugar , one or two tablespoons at a time. Sift the sugar in through a sieve if you haven't sifted already. Mix or beat well each addition.Keep adding the sugar until all the sugar is added. The buttercream will be thick and fluffy. Add the vanilla and beat in well.Add the nutella and beat until smooth.Use as needed!Assembly :Make two chocolate cakes . Using a serrated knife , divide each horizontally into two layers. Place one layer on a plate / cake board . Spread about two tablespoons of the buttercream and spread using a spatula. Place another layer on top and repeat with all layers. Cover top and sides with the Buttercream as smoothly as possible. Pour ganache on top , if desired!Also :If you want to make ganache for the top , chop up 50 grams of dark chocolate in a bowl. Boil 1/4 cup cream in a saucepan / microwave and pour over the chopped chocolate . Let rest for a minute and mix until smooth. Pour over top of cake and smooth . For more details about ganache , you may want to see this.For the smoothest fluffiest buttercream , use room temperature ingredients , sift sugar and add sugar little by little beating well in between.The frosting makes just enough to fill and coat this cake. If you want to put another coat (might be sweetness overload) or pipe , make a double batch!Cake can be stored in an airtight container at room temperature for 3 days or 1 week in refrigerator.Buttercream can be stored in an airtight container at room temperature for 1 day , refrigerator for 4-5 days and freezer for 2 months.Get frosted cake to room temperature before serving.One cake with the recipe amounts given , makes a 5 inch cake that is around 2 inches tall.