Green Goddess Dipping Sauce
Purée mayonnaise, buttermilk, green onion, herbs and mustard until smooth. Slowly pour in oil while blending and season to taste.
Soak bamboo skewers (if using) in water while preparing other ingredients.
Boil potatoes uncovered in salted water until tender, about 12 minutes. Drain and cool to room temperature.
Slice potatoes in half (or leave whole if small). Skewer an onion piece to create a base, and skewer Prosciutto on at one long end. Skewer a piece of potato and onion, then skewer same Prosciutto slice, so it wraps over one side of the potato.
Skewer another potato and onion piece and fold and skewer Prosciutto, again wrapping. Continue this, using a second slice of Prosciutto, until skewer is full (Prosciutto will create a lovely scalloped effect around potatoes & onions).
To heat, lightly brush kebabs with oil and season. On a hot grill, or over an open fire, grill kebabs until warmed through, about 6 minutes. Serve warm with dipping sauce.