In a shallow bowl, combine cracker crumbs and taco seasoning; set aside. In another bowl, combine 3 tablespoons butter, cheese, chilies, onion and salt. Shape mixture into six balls.
Flatten chicken to 1/4-in. thickness. Place a butter ball in the center of each. Roll up and secure with toothpicks. In a shallow microwave-safe bowl, melt remaining butter. Dip chicken in butter, then coat evenly with cracker mixture.
Place seam side down in a greased shallow round 3-qt. microwave-safe dish. Microwave, uncovered, on high for 12-14 minutes or until chicken juices run clear and a meat thermometer reads 170°. Discard toothpicks. Yield: 6 servings.