10 RITZ Crackers, crushed (about 1/3 cup)
1/2 cup milk
1/4 lb. (4 oz.) VELVEETA, cut into 1/2-inch cubes
4 oz. (1/2 of 8-oz. pkg.) PHILADELPHIA Cream Cheese, cubed
4 eggs, separated
3 Tbsp. chopped fresh chives
Heat oven to 375F. Spread cracker crumbs onto bottom of 9-inch square baking dish sprayed with cooking spray. Microwave milk, VELVEETA and cream cheese in large microwaveable bowl on HIGH 1-1/2 min. or until cheeses are completely melted and mixture is well blended, stirring after each minute. Whisk egg yolks and chives until blended. Stir into VELVEETA mixture. Beat egg whites in small bowl with mixer on high speed until stiff peaks form; gently stir into VELVEETA mixture. Pour into prepared dish. Bake 20 to 25 min. or until top is puffed and golden brown. Serve immediately.