Preheat oven to 350ºF (177ºC). Spray a 9X13 inch baking dish with nonstick cooking spray; set aside.
In a large skillet, melt 2 tablespoons butter over medium heat. Stir in shredded cabbage (2 pounds), celery (1 cup), onions (2 1/2 cups), and garlic (2 cloves) and sauté, stirring until vegetables are tender, about 10-12 minutes.
Pour vegetables into the prepared baking dish; set aside.
In a medium saucepan melt the remaining 2 tablespoons of butter over medium heat. Sprinkle flour (2 tablespoons) over the melted butter and whisk constantly, until the mixture is thick and the color of peanut butter, about 1 minute.
Remove pan from heat and add milk (1 1/2 cups) slowly, whisking constantly, until the mixture is smooth and all lumps are broken up. Return to the heat, continue to cook, and whisk constantly, until the sauce has thickened and it begins to bubble, about 3 minutes.
Remove pan from heat and stir in Worcestershire sauce (1 teaspoon), salt (1 1/2 teaspoons), Tabasco sauce (1 teaspoon), pepper (3/4 teaspoon), nutmeg (1/4 teaspoon), and 3/4 cup parmesan. Pour sauce over the cabbage. Use tongs to toss cabbage to evenly distribute sauce.
Sprinkle panko crumbs (1/3 cup) over sauced cabbage then sprinkle 3/4 cup parmesan over the top of the panko.
Place in preheated oven and bake until casserole is bubbly and the top is golden brown, about 20-25 minutes.