Add potatoes to a large pot filled with enough water to cover them by at least 1 inch. Add the salt to the water, then bring to a low boil and cook until the potatoes are tender enough to easily be pierced with a fork, about 15 minutes. Drain well.

While the potatoes cook, heat the butter and cream in the microwave until the butter is mostly melted and the cream is warm, about 60 seconds.

Mash the drained potatoes using a potato masher, then stir in the warm butter and cream. Season with additional salt and pepper to taste.

I found Irish bangers, which are actually already cooked and just need to be heated through. Raw sausages like brats will take longer to cook.

In the same skillet over medium heat, heat the oil butter. Add the sliced onion and sprinkle with the sugar and ¼ teaspoon of the salt. Cook, stirring frequently, until onions are softened and start to caramelize and brown, about 15-20 minutes.

Add garlic, and thyme, and continue to cook and stir for 1 minute. Whisk beef broth and cornstarch together, then add to the pan with the onions, along with the balsamic vinegar, scraping up any browned bits from the bottom of the pan.

Let the onion gravy come to a simmer, then reduce heat to medium-low. Simmer for 3-5 minutes, stirring frequently, until gravy has thickened, then taste and season with additional salt and pepper, as needed. Return the sausages to the pan with the gravy to make sure they are hot.

Serve the potatoes with the sausages, topped with a generous spoonful of the onion gravy. Sprinkle with chopped parsley and serve with green peas.