Wash and dry the produce. Peel potatoes then cut into 1-inch cubes. Set aside. Then slice the onion into small pieces.
In a medium saucepan over medium-high heat, melt 1/2 cup of butter. When the butter is melted, add the sliced onions and sugar. Cook the onions until caramelized, about 30 minutes, stirring occasionally.
Once the onions are a deep golden brown, add the red wine and boil for 1 minute. Reduce the heat and simmer for 10 minutes. After 10 minutes, pour in the beef broth, yellow mustard, Worcestershire sauce, and salt and pepper to taste, and then stir to blend. Bring the sauce to a boil, then once again reduce the heat to a simmer. Cover the pot and continue to cook for 20-30 minutes.
Prepare a cornstarch slurry: In a small cup, mix one tablespoon of cornstarch with one tablespoon of water. After the sauce has cooked, pour the cornstarch slurry into the sauce. Continuously whisk the sauce until it becomes slightly thickened. Continue to simmer an additional 5 minutes. Keep warm.
Meanwhile, preheat the oven to 400 degrees. In a large pot, boil the potatoes in salted water until they are fork-tender, about 15-20 minutes.
While the potatoes are cooking, spray a baking sheet or baking dish with cooking spray. Place the sausage links in or on the pan—roast in the oven 15 minutes, per side. Cook the sausages until completely brown and cooked, and the juices run clear.
Next, drain and then return the potatoes to the pot. Add the cream cheese, remaining butter, milk, and seasonings to the potatoes. Beat the potatoes with an electric mixer or potato masher until smooth, fluffy and well blended.
To serve, place a pile of potatoes on a plate, lay the pork sausages on the potatoes and then pour the onion gravy on top. Garnish with fresh parsley and serve with fresh vegetables if desired. Enjoy!