Boil 2-1/2 lbs. red potatoes until fork tender. When cool enough to handle, peel the skins and discard.
Saute 1/2 red onion in reserved bacon grease until soft.
In a large bowl, whisk together 1/2 apple cider vinegar, 1/4 cup water, 1 tablespoon plus 1 teaspoon granulated sugar, 1 teaspoon black pepper, 1 teaspoon coarse salt, 2 teaspoons coarse ground brown mustard, 1 teaspoon prepared yellow mustard.
Gently toss in potatoes, bacon and onions. Please toss gently or you will have smashed German Potato Salad. Garnish with finely minced flat-leaf parsley and paprika.