HEAT oven to 375°F. 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. Kraft Kitchens Tips: Healthy Living: Save 30 calories and 4g of fat, including 3g of sat fat, per serving by preparing with 2% Milk VELVEETA® and PHILADELPHIA Neufchatel Cheese. Substitute: Prepare using 1/2 tsp. freeze-dried chopped chives.