Prepare the mornay sauce according to the recipe below. Reserve.
In a medium sauce pan, over medium heat, brown the sausage along with the bacon in their own fat (about 3 minutes), stirring occasionally.
Add the onion and sauté until translucent (about 2 minutes). Add the rice and sauté lightly (about 1 minute). Add the stock and the salt, stir, and bring to a boil over medium-high heat. Stir again, cover, and reduce heat to low. Let cook until tender (12 -15 minutes).
Remove from heat, and mix in the mornay sauce and vegetables. Place into a 13" x 9" greased glass pan, layer 2 cups of the cheese on top. Then, make a second layer of rice and finish with the other 2 cups of cheese. Cover with a greased sheet of aluminum foil. Let bake in a preheated oven at 350 F (180º C) for about 25 minutes.
Remove foil and sprinkle the parmesan cheese. Return to the oven, uncovered and let broil until cheese browns, about 3 minutes. Sprinkle the parsley and serve.
Alternatively, remove foil and sprinkle shoestring potatoes on top instead and then, the parsley. Serve immediately.
For the mornay sauce: In a heavy-bottomed saucepan, bring the milk to a simmer over medium heat, stirring occasionally and taking care not to let it boil.
Meanwhile, in a separate heavy-bottomed stainless steel saucepan, melt the butter over medium heat until it becomes frothy.
With a wooden spoon, stir the flour into the melted butter a little bit at a time, until it is fully incorporated into the butter, yielding a pale-yellow-colored paste. Heat this paste (called roux) for another minute or so, to cook off the taste of raw flour.
Using a wire whisk, slowly add the hot milk to the roux, whisking vigorously to ensure that it is free of lumps.
Simmer for about 20 minutes, or until the total volume has reduced by about 20 percent, stirring frequently to make sure the sauce doesn't scorch at the bottom of the pan. The resulting sauce should be smooth and velvety. If it is too thick, whisk in a bit more milk until it is just thick enough to coat the back of a spoon.
Remove the sauce from heat. For an extra-smooth consistency, carefully pour the sauce through a strainer. Mix the cheese. Season the sauce with salt, white pepper, bouillon, and nutmeg. Keep the sauce covered until you are ready to use it.