Heat a small amount of canola oil in a saute pan over medium-high heat. Add the sausage meat and brown. Drain off any excess fat and add spinach. Cook together until flavors integrate and spinach softens, 3 to 5 minutes. Remove from heat and let cool.
Preheat oven to 400 degrees F.
Season mushroom caps with salt and pepper and toss with canola oil. Stuff mushroom caps with sausage/spinach mixture and sprinkle with Parmesan. Brown in oven and serve.