cooking spray
2 1/2 cups cooked, diced chicken (chilled or frozen)
1 (11-oz) can Southwestern- or Mexican-style corn (undrained)
1 (10-oz) can mild diced tomatoes and green chiles (undrained)
1/2 cup corn muffin mix
1/4 cup light sour cream
1/4 cup light mayonnaise
1/4 cup shredded reduced-fat sharp Cheddar cheese

1 (3.4-oz) box instant pistachio pudding mix
2 cups reduced-fat milk
12 chocolate stick cookies
large zip-top bag
1 cup frozen non-dairy whipped topping (divided)