Cube chicken. Blend soup, sour cream, milk and salsa. Place half of the tortilla pieces over bottom of 1- 0.5-quart microwave-safe casserole. Layer w/ half of chicken, onions, cheeses, and sauce. Repeat. Cover. Refrigerate several hours or overnight. Microwave, covered, 12-14 minutes, or until bubbly. Remove from microwave, uncover, and sprinkle lightly with paprika. Allow to stand 5 minutes.