Heat a tablespoon of olive oil in a large skillet over medium heat. Add the bratwurst or Irish sausages, cooking for about 6-8 minutes until they are browned on all sides. Set the sausages aside once done.

In the same skillet, melt two tablespoons of butter. Add the sliced yellow onions with a pinch of salt and black pepper, sautéing for about 10 minutes until caramelized.

Stir in two tablespoons of all-purpose flour, cooking briefly, then deglaze with one cup of Guinness, scraping the bottom. Follow with two cups of beef broth.

Return the sausages to the skillet and let the mixture simmer on low for about 10-15 minutes to allow flavors to meld.

While the gravy simmers, peel and dice the gold potatoes, boil them in salted water for about 10-12 minutes until fork-tender. Drain, return to pot, and mash with three tablespoons of butter and half a cup of warmed whole milk.

To serve, spoon mashed potatoes onto plates, add the sausages, and ladle the Guinness onion gravy over both. Garnish with chopped parsley or green onions.