Preheat the oven to 400 degrees. Line a baking sheet with aluminum foil and place the squash halves cut side up on the baking sheet. In a small dish, combine the melted butter, minced garlic and 1/8 teaspoon of the rubbed sage. Using a silicone pastry brush, brush the butter mixture onto the inside and outside of each squash half. Roast in the oven for 50-60 minutes until tender.

Bring a large skillet over medium heat and add the sausage. Cook, breaking up with a spoon, until meat is cooked through. Remove meat to a mixing bowl and place the pan back on the burner. Add the onion, celery and mushrooms to the skillet and cook for about 3 minutes. Add the apples and cook for an additional 2 minutes. Turn off the burner and add the onion mixture to the sausage in the mixing bowl. Add the remaining 1/8 teaspoon of sage, the panko crumbs and the Parmesan cheese. Season with salt & pepper to taste. Add the egg white and stir until well combined.

When the squash halves are finished roasting, evenly pile the sausage stuffing into the two halves. Return to the oven and cook for an additional 18-20 minutes.