If possible, roast the bacon in the oven at 250-300F for 30 minutes; Recover and reserve the rendered fat. Chop the roasted bacon.
Grate or chop the cabbage finely.
In a stock pot, brown the sausage and onions in bacon fat and olive oil for about 5 minutes. Add the cabbage and continue heating 5 minutes while stirring frequently. Season to taste with salt and pepper. Deglaze with 1/2 of the vinegar and mustard; Reduce the liquid until dry. Add the stock, potatoes, the remainder of mustard and vinegar and bacon. Stir in the sauerkraut. Bring the contents of the pot rapidly to a rapid boil. Cut the heat, and simmer for 30-35 minutes.