Preheat the oven to 425 degrees F.

Spray a sheet pan with olive oil spray, and place the mushroom caps onto the pan with the stem side facing up.

Roast the mushrooms for 10-15 minutes, until the caps fill with liquid. Then turn them over, spilling the liquid onto the sheet pan. Cook the mushrooms for another 10 minutes, until the liquid evaporates.

Remove the mushrooms for the oven and set aside while you make your filling.

To make the filling, saute the turkey sausage in a non-stick pan, until the sausage is browned and cooked through. Remove the cooked sausage from the pan and set it aside to cool.

In the same pan, saute the minced garlic clove and spinach, until the spinach is wilted and the liquid has evaporated from the pan. Remove the cooked spinach and garlic from the pan and set it aside to cool.

Finally, finely chop up the reserved mushroom stems and saute them, until they're browned and cooked through.

Combine the sausage, spinach, mushroom stems, cream cheese, gruyere, parsley and 1 tablespoon of breadcrumbs in a bowl, and stir to combine. Check the mixture for seasoning, and season with salt and pepper to taste.

Stuff the mushrooms with a heaping spoonful of the filling, depending on how big they are, you'll use varying amounts of filling per mushroom. Sprinkle the mushrooms with the remaining breadcrumbs.

Switch the oven to broil and broil the mushrooms at 375 F for 5-7 minutes, or until the breadcrumbs are golden brown.