"This recipe was a huge favorite at a local restaurant for many years. Unfortunately, the family who owned the restaurant is no longer in town, but I enjoyed this so much I counted myself lucky to get a copy before they left! Be sure to thaw the spinach out the night before for more even cooking."
Preheat oven to 375 degrees. Brown turkey sausage and fennel in large saucepan. Drain excess grease. Add mushrooms and spinach. Place turkey mixture in a greased 9x13 casserole dish, or use several individual size serving dishes for better serving appearance.
In large bowl, mix butter, Parmesan cheese, half and half, Monterey Jack cheese, dry mustard and vermouth. Pour over turkey mixture.
Bake for 10-15 minutes, or until cheese is golden and bubbly.