For the Cake

1. Preheat oven to 160C (150C if its a convection oven). Grease and line a 6 or 7 inch cake pan.
2. Mix together yogurt and powdered sugar to form a smooth mixture.
3. Add baking soda, baking powder and salt to the yogurt mixture and mix well. Let it rest for 5 minutes. You will notice many air bubbles on the surface of the yogurt.
4. Add oil and vanilla extract to the yogurt mixture and mix well.
5. Add flour and unsweetened cocoa powder and mix gently to form a smooth, lump free batter. Do not overmix or you will end up with a bread-like texture.
6. Add to the prepared baking pan and bake at 160C for 30-35 minutes or until the cake is fully cooked through.
7. Let the cake cool completely. Remove from the mold and set aside.

Chocolate Marshmallow Frosting

1. In a microwave safe bowl, add all the ingredients (butter, chocolate, chopped marshmallows and cream) and microwave on full power for 5 minutes. Every 1 minute, remove the bowl and mix everything to avoid burning. Keep microwaving and stirring until you have a frosting-like consistency. Set aside to cool

Putting it together

1. Spread the chocolate frosting on top of the sponge cake. You cake make a layered cake or ever spread the frosting all over the cake or just the top.