Cut the potatoes into pea-size cubes and in a steamer set over boiling water steam them, covered, for 4 to 8 minutes, or until they are just tender.
Transfer the potatoes to a bowl, add the onion, and toss the mixture with salt and pepper, to taste.
In a skillet cook the bacon over moderately-low heat, stirring, until it is crisp and transfer it with a slotted spoon to paper towels to drain.
Pour off all but 2 tablespoons of the fat from the skillet, to the remaining fat add the flour and the sugar, and cook the mixture, stirring, for 30 seconds.
Add the vinegar and ¼ cup water, bring the mixture to a boil, whisking, and whisk in the mustard.
Pour the dressing over the potatoes mixture, add the eggs, peas, parsley, and bacon, and toss the salad well. Serve the salad warm or at room temperature.