Heat oven to 375°F. Brush large cookie sheet with 1 teaspoon of the oil; sprinkle evenly with cornmeal. Unroll pizza crust dough on cookie sheet; press dough into 14x12-inch rectangle. Brush dough with remaining 1 teaspoon oil. Bake 10 to 14 minutes or until light golden brown.
Spread Alfredo sauce evenly over partially baked crust. Sprinkle with cheeses, chicken, mushrooms, onion, walnuts and garlic.
Bake 10 to 18 minutes longer or until crust is golden brown. Sprinkle with basil.