Heat the butter in a heavy-bottomed pan until just melted. Add the other two ingredients. Stir to combine. Bring to a gentle boil and cook until the mixture thickens and the sugar is dissolved (around 6-8 minutes). Stir occasionally to prevent sticking/burning.
Take 2 x 56g bars of Daim and blitz them in a food processor. Remove half when they are crushed but still chunky and set to one side. Continue to blitz the remaining Daim until they resemble a powder. Again, set to one side (but separate from the larger bits).
Pre-heat the oven to 175ºC (350ºF) and prepare two 6 inch (18cm) pans.
Cream the butter, sugar and Daim "powder" together until light and fluffy. Beat in the eggs and then the butterscotch and dark syrup. Finally, mix in the milk and Greek yoghurt.
In a separate bowl, combine the flour, baking powder, vanilla sugar and baking soda and then stir into the wet ingredients. Pour into the prepared pans and bake for around 30-35 minutes. The cakes are ready when an inserted skewer comes out clean.
Let the cakes cool a little before turning out onto a wire rack. Allow the cakes to cool completely.
Beat the butter and cream cheese together until nice and light. Add the remaining butterscotch. Finally, add as much icing sugar as needed to make a thick but spreadable frosting.
Carefully cut both cakes in half. Spread an even amount of frosting over the top of every layer and place the cakes on top of each other. If you like, give the cake a bit of a "naked" look (as I have) but it isn't necessary.
To decorate the cake, break up the remaining 56g of Daim aiming for a jagged edge and stick them into the frosting. Sprinkle with the retained crushed Daim. I also added a few gold sprinkles I had in the cupboard, but these are optional. Slice and enjoy!
Please note - I use grams and weigh my ingredients. The conversions have been taken from online sources and have not been verified by myself; therefore, measurements may not be entirely accurate.