Twice-Baked Potatoes with Goat Cheese and Chives

Position rack in center of oven; preheat to 375°F. Rub oil over potatoes. Pierce in several spots with fork. Place directly on oven rack; bake until very tender, about 45 minutes. Transfer to rack; cool 10 minutes. Using oven mitts, grasp 1 potato in hand. Using serrated knife, cut off top 1/4 of potato. Using spoon, scoop out potato, leaving 1/2-inch-thick shell; transfer potato flesh to large bowl. Repeat with remaining potatoes. Mash potatoes until smooth. Mix in cheese, then half and half, butter, and chives. Season with salt and pepper. Spoon about 3/4 of potato mixture into shells, dividing evenly. Transfer remaining potato filling to pastry bag fitted with large star tip. Pipe filling atop potatoes. Place potatoes on baking sheet. (Can be made 1 day ahead. Cover loosely with plastic wrap and refrigerate.)Position rack in center of oven and preheat to 375°F. Bake potatoes until filling is heated through and tops brown, about 20 minutes.