Preheat the oven to 350f and grease 8 mini bundt cake tins using cake release spray.
In a bowl whisk together the flour, baking powder, baking soda and salt and set aside.
In a stand mixer beat the half cup of butter until light and fluffy then add in the brown sugar and beat again until fluffy.
Add the eggs one at a time followed by the vanilla extract.
Alternate adding in the flour and sour cream both starting and ending with the flour.
Mix until just combined then fold in one cup of chocolate chips.
Spoon the batter into a piping bag then pipe into the bundt tins.
Bake for around 25 minutes until the top of the cakes springs back when pressed and when a toothpick inserted into the centre of the cakes comes out clean.
Allow to cool in the tins for five minutes before turning out onto a wire rack to cool completely.
Once cooled, place the remaining chocolate chips with the three tablespoons of butter into a pan over a low heat and melt until smooth and glossy.
Spoon over the mini cakes and serve.