Freeze the coconut milk first. I pour it into ice cube trays, then measure out the cubes. Slowly sprinkle the lye over the cubes, and stir, stir, stir. The lye solution will be thicker than when mixed in water as some of the fat in the milk start to react with the lye. Once it's cooled down, proceed with your soapmaking as usual. This has worked for me, but others may have another way.