Preparation

Place potatoes in a 4-quart saucepan with the garlic, vinegar, 1 teaspoon of the salt and water to cover by 1 inch. Bring to a boil then reduce to a simmer and cook until potatoes are tender, about 15 to 20 minutes. Drain.Coat a 3-quart ceramic baking dish (about 3 to 4-inches high) with ½ tablespoon of the butter. Preheat oven to 350°F.Insert the medium (4-mm) slicing disc in the Cuisinart® Food Processor. Arrange the onions in the large feed tube, cut side down and use medium pressure to slice. Melt 1 tablespoon of the butter. Toss sliced onion with the melted butter and ½ teaspoon of the kosher salt. Reserve.Insert the metal “s” blade. Place the cream cheese, milk and egg in the work bowl. Process to blend until smooth and homogenous, about 1 minute. Transfer to a large bowl and reserve.Insert the medium shredding disc. Working in several batches, place the drained potatoes and garlic in the large feed tube and use light pressure to shred. Transfer to the large bowl with the cream cheese mixture. Add remaining teaspoon of salt and the pepper. Stir to blend. Spoon the potatoes into the prepared baking dish. Top the potatoes with the buttered, sliced onions, and cover loosely with aluminum foil. Place in preheated 350°F oven and bake for 25 minutes. Remove foil and continue to bake 30 to 35 minutes longer until puffed and the onions are golden. Serve hot.Baked Mashed Potatoes may be prepared up to 2 days ahead. Cover and refrigerate. Remove from refrigerator and let stand at room temperature 30 minutes before baking.