Scrub potatoes. Prick several times with a fork. Place in a microwave-safe shallow dish. Micro-cook on 100 percent power (high) for 8 to 10 minutes, or until tender, rearranging once. Cool slightly. Cut a lengthwise slice 2 inches wide from the top of each potato; discard skin from slice and place pulp in a medium bowl. Scoop pulp out of each potato, leaving a 1/4-inch shell. Add the pulp to the same bowl. Mash the potato pulp with a potato masher or an electric mixer on low speed. Add cream cheese, balsamic vinegar, onion, soy sauce, garlic powder, and pepper. Beat or stir until smooth. Add ham. (If desired, stir in a little milk to make of desired consistency.)
Spoon the mashed potato mixture into the potato shells, pressing gently. Return to baking dish. Micro-cook, uncovered, on 100 percent power (high) for 4 to 5 minutes more or until heated through. Sprinkle with chives. Makes 2 main-dish servings.