Gather all your ingredients so that you have everything close at hand on the counter or table.
Prepare the Ingredients
Using a cutting board and Chef's knife, slice the onion. Mince the garlic.
Begin preparing the mashed potatoes, as directed by their recipe.
Cook the Sausages
Meanwhile, heat 1 tablespoon extra-virgin olive oil in a large saute pan over medium-low heat. Add bratwurst sausages and place lid on skillet. Cook for 4-5 minutes on each side until sausages reach an internal temperature of 150 degrees. Remove sausages and cover with foil to keep warm. If unable to fit all of the sausages in the pan at once, repeat with the remaining bangers.
Prepare the Onion Sauce
Add another tablespoon of extra-virgin olive oil and butter to the pan and saute the sliced onion and minced garlic, until golden brown, about 3-4 minutes.
Stir in the all-purpose flour to make a roux. Add half of the beef stock and the beer, stirring until combined. Cook over low heat, stirring every few minutes until the gravy thickens. Add the remaining stock and continue to cook until gravy thickens to desired consistency.
Season with kosher salt and freshly ground black pepper. Add cooked sausages to the gravy. Cover to keep warm until the mashed potatoes are finished as directed by their recipe.
Serve sausages and gravy over mashed potatoes. Serves 4-6.
Notes
*Unless otherwise indicated, all butter on this recipe site is salted.