4 links pork sausage, 2 pounds potatoes (peeled and cubed), 1/4 cup butter, 2 tablespoons milk (optional), 1 teaspoon dry mustard powder, salt and ground black pepper to taste, 1 tablespoon butter, 2 large onions (chopped), 6 cups beef broth, 2 cups red wine

4 links pork sausage, 2 pounds potatoes (peeled and cubed), 1/4 cup butter, 2 tablespoons milk (optional), 1 teaspoon dry mustard powder, salt and ground black pepper to taste, 1 tablespoon butter, 2 large onions (chopped), 6 cups beef broth, 2 cups red wine

Preheat oven to 200 degrees F (95 degrees C).
Cook the sausage links in a skillet over medium-low heat until browned on all sides, about 5 minutes per side; transfer to an oven-safe dish and move to the preheated oven to keep warm.

Place potatoes into a saucepan over medium heat, cover with water, and boil gently until potatoes are tender, 10 to 15 minutes. Drain and allow to steam dry for a minute or two. Mix in 1/4 cup of butter, milk, dry mustard, salt, and black pepper; mash until fluffy and smooth. Set aside.

Melt 1 tablespoon butter in a skillet over medium-high heat; cook the onions until translucent and just starting to brown, about 8 minutes. Pour in the beef broth and red wine; boil the mixture down to about half its volume, about 10 minutes. Season with salt and black pepper.

To serve, place a sausage onto a serving plate with about 1/2 cup of mashed potatoes. Pour the onion gravy over the sausage and potatoes.