Place the cabbage in a large mixing bowl. Add the bacon to a medium sauté pan and set over medium heat. Render the bacon fat and brown the bacon, adjusting the heat as needed. Remove the bacon with a slotted spoon to a plate lined with paper towel, then pour off all but 2 tablespoons bacon fat (approximate, don’t measure) from the pan.
Set the pan over medium low heat. Add the flour and stir until smooth. Cook for 1 minute. Stir in the vinegar and water and bring to a boil. Season with the salt. Gradually – and slowly! – whisk this mixture into the egg.