Preheat the oven to 400 degrees F.

Lay the honeynut squash halves onto 1 large or 2 smaller-sized baking sheets. This will depend on what size sheet pans you have in your house.

Rub the inside flesh of the squash with olive oil and sprinkle them with the desired amount of kosher salt and black pepper.

Flip the squash over so the cut side is down.

Roast for 20-25 minutes or until the squash flesh is soft.

While the squash is cooking add a 12-inch skillet over medium-high heat and add the Italian sausage.

Break up the sausage with a spatula so it can be evenly brown and no large chunks remain.

When half of the sausage is browned add in the diced onions and mushrooms.

Continue cooking until the sausage is fully cooked and the onion and mushrooms are soft.

Add in the garlic and let cook for 30 seconds or until fragrant.

Remove from heat and set aside.

When the squash is fully cooked let it cool slightly so you can safely handle it.

Scoop out the flesh of the squash in a large bowl but leave a small amount of the flesh around the skin of the squash so it can hold its shape.

Put the squash back onto the baking sheet and place them into the oven to cook the shell a little longer while you prepare the filling, about 5 minutes.

Stir the scooped-out squash so it's smooth. Add in the cooked sausage mixture, the chopped baby spinach, and 1/4 cup of the Parmesan cheese.

Take the squash out of the oven and fill each squash half with the filling. Smooth the top.

Sprinkle 1/2 tablespoon of the remaining Parmesan cheese on the top of the stuffed squash halves, place in the oven, and bake for another 10 minutes to heat up the filling and brown the top.