Bring a large pot of lightly salted water on to boil. Meanwhile, prepare the squash by peeling/cutting off the hard skin. Cut in half and scoop the seeds out, then chop into 1/2 inch cubes. Cook the squash in the boiling water until knife tender, roughly 6-10 minutes. Add in the raisins for the last minute of cooking. Rather than just testing with a knife, take a piece out and try it to be sure you like the consistency. Strain and rinse well under cold water to cool everything down - set aside.