Step 1

Put the sweet potatoes in a large saucepan and cover with 2 inches water. Add 2 tablespoons salt. Bring to a gentle simmer and cook until the sweet potatoes are knife-tender, 10 to 15 minutes. Drain well and put in a large bowl. Keep warm.

Step 2

Meanwhile, cook the bacon in a large nonstick skillet over medium heat until crisp, 8 to 10 minutes. Remove the bacon from the grease and set aside on a paper towel-lined plate, leaving the grease behind in the skillet. Return the skillet to medium-low heat, then add the onions and cook until translucent, about 10 minutes.

Step 3

Stir the mustard and vinegar into the skillet with the onions, then whisk to combine. Let the dressing simmer for a minute, then pour over the sweet potatoes in the bowl. Add half of the bacon and toss to coat evenly. Season with salt and pepper.

Step 4

Transfer the sweet potato salad to a serving platter and garnish with the remaining bacon and parsley. Serve hot or chill to serve cold.