Preheat the grill. Place the beer in a saucepan, over medium heat. Bring the liquid to a boil. Add the sausages and cook for 10 minutes. Remove from the sausages from the liquid, reserving the liquid. Set the sausages aside. In a large saute pan, over medium heat, render the bacon until crispy, about 6 to 8 minutes. Remove the bacon and set aside. Discard the all the bacon fat except for 1/4 cup. Place 1/4 cup of the fat back into the pan and add the onions. Season with black pepper. Saute for 2 to 3 minutes, or until tender. Add the cabbage. Season with salt and pepper. Continue to saute for 4 minutes or until the cabbage is tender. Stir in the garlic, mustard and 2 cups of the liquid from the sausages. Bring the liquid to a simmer and cook for 8 to 10 minutes, stirring occasionally. Reseason with salt and pepper. Place the sausages on the grill and cook for 2 minutes on each side. To serve, place the sausages between each bun. Top each sausage with some of the smothered cabbage.
Preheat the oven to 400 degrees F. In a mixing bowl, toss the potatoes and garlic with a drizzle of olive oil. Toss well. Season with salt and pepper. Place on a baking sheet and roast for 15 minutes. Remove from the oven and cool completely. Using a mini food processor, combine the mayonnaise, mustard and lemon juice. Process until smooth. Season with salt and pepper. Add the parsley and continue to process until incorporated. In a mixing bowl, toss the roasted potatoes and garlic, mayonnaise, sliced eggs, bacon and red onions. Mix well. Season with salt and pepper. Cover with plastic wrap and refrigerate for 2 hours. Remove from the refrigerator and mix the salad. Reseason with salt and pepper if needed.