Very very carefully, cut the spaghetti squash in half lengthwise. Cutting this in half is the hardest part because the skin of the squash is super hard.It may be best when buying the squash to ask a produce department employee to cut it in half lengthwise for you.
Preparing the Squash - with a large spoon, scoop out and discard the pulp and seeds from the middle of the squash. Add water in the cavity of the squash.
Cooking the Squash - set the squash, cavity side up on a microwave-safe plate. Wet a paper towel and drape it over the top of the squash. Cook until done (should be about 7 minutes). While the squash is cooking start the mushrooms.
Remove the squash along with the plate from the microwave and let sit on a cutting board or hot plate (the plate with the squash on it will be hot); keep it covered with the paper towel. Let it sit for 5 minutes (it should continue to steam inside of the cavity).
Removing the Strands of Spaghetti Squash - use a fork to scrape the inside of the squash from the skin side towards the middle cavity until all of the “spaghetti strands” are separated from the skin.