Place the first 7 ingredients in food processor and puree. Transfer this mixture to a small pot and simmer 3 to 4 minutes, until lightly thickened. Season with salt, and then cool to room temperature. Cover and chill the sauce in the fridge until needed.
Preheat an indoor or outdoor grill to medium-high. Brush the prawn kabobs with the oil; season with salt and pepper. Grill the kebabs 1 to 2 minutes per side, or until just cooked through and bright pink. Place 2 kabobs on each of 4 plates and place a bowl of the sauce alongside for dipping.
Note: To peel the peaches, cut a small star into the blossom end. Plunge the peaches into boiling water for 1 to 2 minutes. Cool in cold water and slip off the skins.
Recipe Options: Serve the sauce with other grilled seafood, such as halibut steaks or large scallops. Give the sauce an additional taste element by mixing in one or two tablespoons of chopped fresh cilantro or thinly sliced green onion. To make sweet and sour nectarine sauce, simply replace the peaches with nectarines.