01 -
Boil peeled potatoes in salted water until fork-tender, then drain thoroughly. Mash with butter, warm milk, and season to taste until smooth and creamy. Keep warm for serving.
02 -
Heat olive oil in a large sauté pan over medium-high heat. Arrange sausages in a single layer and cook, turning occasionally, until uniformly browned and fully cooked. Transfer sausages to a clean plate and set aside.
03 -
Retain approximately 2 tablespoons of sausage drippings in the pan; discard excess. If needed, supplement with butter. Add 2 tablespoons butter and the sliced onions. Sauté for about 4 minutes, stirring occasionally, until onions are mostly softened. Sprinkle in the flour and cook for 1 minute, stirring continuously to combine.
04 -
Pour in white wine, scraping any browned bits from the pan. Slowly whisk in the beef stock until smooth. Add garlic powder, balsamic vinegar, and Dijon mustard. Stir and let simmer for 1-2 minutes, until the gravy thickens. Thin with extra beef stock if needed. Adjust seasoning with salt and pepper to taste.
05 -
Arrange mashed potatoes on each serving plate, top with sausages, and spoon onion gravy generously over the top. Garnish with fresh parsley and accompany with peas. Serve immediately.