Spray 13x9-inch (3-quart) glass baking dish with cooking spray. Spread cream cheese evenly on 1 side of each bread slice. Sprinkle 12 slices with chocolate chips. Top with remaining 12 bread slices, cream cheese side down, to make 12 sandwiches.
In medium bowl, beat milk, brown sugar and eggs until blended. Dip each sandwich in egg mixture, coating completely. Place dipped sandwiches in baking dish. Pour remaining egg mixture over bread. Cover; refrigerate 8 hours or overnight.
Heat oven to 350°F. Uncover baking dish; drizzle melted butter over French toast. Bake 40 to 45 minutes or until golden brown. Sprinkle with powdered sugar.