Preheat the oven to 200C/180C Fan/Gas 6. Line your mini loaf tin (see notes for tips)
In a large bowl, or the bowl of a stand mixer, combine the butter, Biscoff spread and sugar for 3-5 minutes on a medium/high speed. Add the eggs and mix again.
Add the flour, baking powder and baking soda. Fold together before adding the milk to thin the cake batter a little. Distribute the mix evenly into the lined tin and bake for 20-25 minutes, until a skewer inserted comes out clean. Let cool.
Make the frosting by combining the butter and Biscoff spread on a high speed with an electric mixer for several minutes. Add half of the icing sugar and beat to combine. Continue to add more icing sugar until you reach the desired consistency. Spread or pipe over the cakes. Decorate with Biscoff biscuits and serve!