-1 lb. small yellow potatoes
-1/4 med. sweet onion, thinly sliced
-1/2 c. red wine vinegar, divided
-Salt and black pepper, to taste
-4 T. olive oil
-1 1/2 T. coarse-ground mustard
-1 head radicchio, cored and chopped
-1/4 c. chopped parsley
Simmer potatoes covered in water until tender, about 15 minutes. Drain potatoes, cut in halves or quarters and place in large bowl with onion.
In small bowl whisk together 1/4 cup vinegar, oil, mustard and salt and pepper to taste; pour over potatoes and toss.
Fold in radicchio and remaining vinegar, to taste.
Season with salt and pepper, fold in parsley.
Serve immediately, or cover and chill up to 6 hours. Enjoy!