Preheat oven to 350°. Drain artichoke hearts, reserving 1/4 cup of juices. Coarsely chop; combine with chicken, tortellini, mayonnaise, 1 cup cheese and reserved artichoke liquid. Place artichoke mixture in a greased 13×9-in. baking dish; sprinkle with remaining cheese.
Bake until bubbly and starting to brown, about 30 minutes. If desired, garnish with basil.