1Line bottom and sides of 8-inch square pan with foil, leaving edges of foil hanging over 2 sides of pan for easy removal later; spray foil with cooking spray.
2In 2-quart saucepan, heat dulce de leche and chocolate chips over low heat, stirring constantly, until chocolate is melted and mixture is smooth (mixture will be very thick); remove from heat. Quickly stir in vanilla. Stir in 2 cups caramel popcorn. Spread in pan.
3In medium microwavable bowl, microwave caramels and cream uncovered on High 2 minutes, stirring every 30 seconds, until melted and smooth. Very slowly pour caramel mixture over fudge layer, and gently spread to cover. Sprinkle with salt and 1 1/2 cups caramel popcorn; press gently so it sticks. Refrigerate until firm, about 2 hours. Cut into 1-inch squares (8 rows by 8 rows). Store covered in refrigerator.