I thought about doing something like this a while back, but the practical implementation of this are hard to achieve in your average garage workshop.
I would suggest having a look at this:
It's an engineering fluid that boils at around 34oC and provide some serious amounts of cooling.
Assuming you used a different coolant that this company makes with a lower boiling point you could enclose that and use it as an intermediate step, but if your cooling is insufficient (remember you're cooling something in the gas phase, heat transfer will be poorer so you need either a large delta or more surface area) it will all boil, increase the pressure, maybe leak and kill your heat transfer from the CPU.
This isn't a project I would take on lightly.