Step 1

Prep: Preheat the oven to 375F degrees. Remove the stems from the portobellos, chop finely and add to the ground beef. With a spoon, scrape out the gills on the underside of the mushrooms and discard. Chop the spinach and grate the cheese.

Step 2

Assembly: Season the mushrooms with a sprinkling of salt and pepper. Mix the cheddar cheese and spinach into the ground beef. (I used my hands. I also added 1/2 teaspoon of salt and 1/2 teaspoon of pepper.) Form two patties and press them onto the portobello mushrooms.

Step 3

Cook: Place the stuffed mushrooms on a small sheetpan or baking dish and cook for 20 minutes. Add the Parmesan cheese to the top of each and pop back into the oven to melt the cheese or under the broiler to brown it.