As you cook the onion, use that time to chop the other vegetables to save time.

Heat a large sauté pan on medium heat. Once that heats up, add olive oil. Once the oil shimmers, add the chopped onion and sauté for 7 minutes or until translucent. Stirring occasionally.

Add salt, pepper, crushed garlic and stir and cook for 1 minute.

Add mushrooms, stir and cook for 2 minutes.

Add chopped spinach, thyme, and stir and cook for 1 minute or until the spinach wilts. Set aside to deal with the pork.

Preheat oven to 350 F.

Unwrap the pork and place it on its side on a cutting board. Take a sharp knife and butterfly the meat – cut it on the equator but not all the way through. Leave an inch between the edge and where you stop cutting. Open it like a book and place it back on the cutting board.

Most likely the pork won't be equal thickness so place a few pieces of plastic wrap on the pork, take a meat tenderizer and pound it with the side of the meat mallet until the thickness looks more uniform.

Sprinkle on kosher salt, garlic powder and spread the mustard evenly on the pork.

Sprinkle on the shredded cheese, walnuts, and apple chunks.

Lastly, spread on the vegetable mixture. Fold the pork back on itself like a book and secure it with either some metal skewers like I did, or use kitchen twine.

lace the pork on the rack of the roasting pan with the fat cap facing up. Add the meat thermometer, and bake for 70 – 80 minutes. The internal temperature should be 145 degrees Fahrenheit.

Slice and Serve.