Melt the 10g butter and using a brush, slather it all over a 1½ litre cake pan. I used the kind we have in Sweden for making sugar cakes, but you can use a bundt or savarin.
Pre-heat the oven to 175°C.
Melt the 100g butter and set to one side.
Beat the sugar and eggs together until light and fluffy.
Combine the flour, vanilla sugar and baking powder and add to the wet ingredients.
Lastly, add in the butter and milk and mix just until combined.
Mix the brown sugar and cinnamon together. Pour half of the batter into the prepared pan and sprinkle over the cinnamon mixture. Using a knife, swirl the sugar into the batter. Pour over the remaining batter.
Bake for around 35-40 minutes, until an inserted skewer comes out clean. Please bear in mind that if you are using a deeper pan, it might take longer to bake.
Leave the cake in the pan until completely cold (it's very soft and a little delicate) and then turn out. Sprinkle with pearl sugar or icing sugar. Slice and enjoy!