French Potato Salad With Tarragon Vinaigrette

• 700 gr potatoes (red)
• 80 ml wine vinegar
• 60 gr onion (chopped red)
• 30 ml olive oil
• 26 gr parsley (chopped fresh)
• 16 gr grainy
• 2 gr tarragon (dried)
• 5 slices mm
• some pepper to