Slice cucumber into ½ inch pieces. Bring to a boil vinegar, water, salt and sugar. Fill a pint jar (or a bowl) with garlic, mustard seeds and fresh dill, add the cucumber. Pour the hot vinegar mixture over the top. Set aside. *See notes.
Put chopped potatoes and salt in a large pot and cover by about an inch with cold water (see notes). Bring to a boil over high heat and reduce to a simmer for 10-15 minutes or until fork tender. Drain and let cool to room temperature.
In a large bowl, mix together yogurt, mayonnaise, pickle brine, dijon, salt and pepper.
Add onion, celery, dill and cooled potatoes to the dressing. Mix and refrigerate 1 hour or up to one day. Refrigerate the quick pickles in their jar separate from the salad (or taste first and if you like a milder pickle add them now-my preference!).
To serve, mix the pickled cucumbers in with the salad. Adjust seasoning adding salt, pepper or more pickle brine as desired. Sprinkle with more fresh dill and chopped chives.
