I use the boiling method. I know it's not very popular nor traditional, but for me, it makes a little Kava go a lot further. And that's important as I live in a place where Kava is difficult and expensive to obtain. Here's my method:
1. Add Kava to a pan and pour over a little boiling water and milk, leave to cool for a few minutes (this will soften the Kava ready for blending)
2. Add cold water to pan, use hand blender to break up the kava pieces for more efficient extraction.
3. Bring to a rolling boil and then shut off the heat and cool rapidly (I transfer the liquid to a cold pan to help with this).
4. Strain through a mesh (I use 200 micron).
5. Enjoy!
Because this method releases so much starch, it with be a thick consistency. It seems to take a long time to cool as well, far longer than hot water, so careful not to burn yourself whilst straining! You can freeze the left over Kava from the mesh and collect it for future use, though as this method is quite efficient, you'll need quite a lot of left over for a potent grog. Bula!