Method:
In a large saucepan, bring ale to a simmer and add bratwurst. Simmer until cooked through, 25 to 30 minutes. Meanwhile, place sliced potatoes in cold salted water in a large pot and bring to a boil. Cook until fork tender, yet not so soft they fall apart, 8 to 10 minutes. Drain and set aside.
In a sauté pan, fry bacon until crisp. Crumble and set aside. Pour off all but 2 tablespoons of bacon fat. Over medium heat, whisk flour into the bacon fat and cook until thickened, 2 to 3 minutes. Stir in sugar and mustard, followed by water and vinegar. Cook, stirring frequently, until thickened, 1 to 2 minutes. Remove from heat, stir in potatoes and bacon and toss gently to coat. To serve, slice bratwurst and divide among plates. Serve with potato salad.