Preheat the oven to 200 degrees.

For the mashed potatoes:

In a large saucepan over medium heat, place the cubed potatoes and cover them with cold water.  Bring to a boil and cook the potatoes until tender – about 15 minutes.

Drain the potatoes in a colander and place them back into the saucepan.

Place the saucepan back on the stovetop over low heat.

Use a potato masher to mash the potatoes.  Add ¼ cup of butter, cream, sour cream, mustard, 1 teaspoon of salt, and pepper.  Mash until fluffy and smooth.  Set aside.

For the bangers:

Meanwhile, while the potatoes boil, place a deep skillet over medium heat and melt the bacon fat, butter, or oil.  Brown the sausages on all sides – about 5 minutes per side.  Transfer the sausages to a casserole dish and place them in the preheated oven until needed.

Melt the tablespoon of butter in the same skillet that you’ve browned the sausage.

Add the onions and cook until they are translucent and beginning to caramelize – about 10 minutes. Stir in the dried thyme and cook another minute.

Whisk in the beef broth, Guinness,  wine, and Worcestershire sauce.  Bring the mixture to a boil.  Stir in the cornstarch slurry. Allow the mixture to simmer until thickened and slightly reduced – about 15 minutes. Season to taste with salt and pepper.

Nestle the sausages into the sauce and turn to coat.  Allow them to simmer for 5 minutes.

For the peas:

Microwave the frozen peas per the package directions.

In a small skillet, melt 1 tablespoon of butter over medium heat.  Add the garlic powder and peas. Season with salt and pepper to taste.

Saute, stirring to coat the peas, for 3-4 minutes.

To serve:

Divide the mashed potatoes evenly among four serving bowls.

Top one side of the mashed potatoes with two sausages.  

Place the peas on the other side of the bowl over the mashed potatoes.

Spoon the sauce and onions over the sausages.

Serve hot.