Pre-heat your oven to 150C Fan/170C/325F/Gas Mark 3, and grease and flour a 10" x 3.5" (2.4 litre capacity) bundt tin
Make the peanut butter cheesecake filling first by whisking together the ingredients until smooth. I used an electric whisk but you can do it by hand too. Set the mixture aside
For the chocolate sponge, mix the butter and sugar together until smooth
Add the eggs and the vanilla extract, and whisk in well
Add the yoghurt and whisk in well
Add the self raising flour, cocoa powder and baking powder. Whisk in gently until you can't see any flour anymore
Pour half of the chocolate cake batter into the tin, then add the cheesecake filling without letting it touch the sides of the tin
Then add the remaining chocolate cake batter on top. Completely cover the cheesecake filling, but try not to disturb it
Bake for 55 minutes or until a skewer inserted comes out clean
Remove the cake from the tin by placing a cooling rack on top of the tin and flipping it over then removing the tin. Leave to cool completely
Once the cake is cool drizzle over the peanut butter (I warmed it in the microwave for 20 seconds to make it easier to drizzle) then drizzle over the melted milk chocolate
Add peanut butter cups, and/or Reese's Pieces on top as desired
Leftovers will keep in an airtight container for 3 days