Peel potatoes, and cut into1/8-inch-thick slices. Set aside.
Melt butter in a large skillet over medium heat. Add onion, tomatoes, and garlic; saute until tender. Add flour, stirring until blended. Gradually add whipping cream, milk, and cream cheese, stirring until smooth. Stir in chives and next 4 ingredients; cook, stirring constantly, 3 minutes.
Combine potatoes and cream sauce into a lightly greased 11- x 7-inch baking dish.
Bake, covered, at 375° for 1 hour. Sprinkle with Asiago and Parmesan cheeses; bake, uncovered, 15 more minutes or until potato is tender.