1) In a bowl, add butter.
2) Place over hot water to melt.
3) Add brown sugar to dissolve into the butter mixture.
4) Place over low heat to cook for 2 minutes, by constant stirring.
5) Pour in milk and bring the mixture a boil, by stirring.
6) Remove from heat.
7) Immediately add the icing sugar to beat in.
8) Serve with applesauce or spread on spice cake.