Say: put some water in the mug with the soap and microwave it all for 30 seconds or so? Seems like it would make for a nice hot-lather shave.
My mother was a barber and the shop was part of the first level of the house. She had a machine which took what I now know to be standard shaving soap cakes and whipped it into a great lather before dispensing it very hot out the front of the machine.
I guess it kept the little tank of water hot all the time and then whipped up the hot lather on demand.
But now that there are microwave ovens - is anyone using them to make hot later with?