Preheat oven to 300 degrees.
In a large Dutch oven, cook the bacon on medium heat until crispy. Remove the bacon using a slotted spoon and drain on paper towels. Sear the sausage (or bratwurst) in the bacon grease to brown. Remove the sausages from the pan to drain with the bacon.
Remove all but about 1/4 of bacon grease from the pan. Add the sliced onion to the pot, and cover. Cook for about 7 minutes, stirring once or twice. Add in the chicken broth, apple cider vinegar, minced garlic, and a sprinkling of pepper. Bring to a boil, then remove from the heat. Pour the onion/broth mixture into a separate dish for a moment.
Layer the sliced potatoes along the bottom of your Dutch oven. Pour the onion/broth mixture over top. Add in 1/2 of the cooked bacon and 1/4 cup of chopped fresh parsley. Place the whole sausages on top.
Cover, cook for 45 minutes. Remove from the heat and pour in 1 cup of Guinness beer (or broth). Replace the cover and return to the oven for another 45 minutes.
Top with the remaining bacon and a few more sprinkles of fresh parsley once it's done. Serve with crusty bread to sop up the au jus.
*If you want all your bacon crispy, then save it all for the end.
