Place crackers in a single layer in a foil-lined 15-in. x -10-in. x 1-in. baking pan. In a large saucepan, bring butter and sugar to a boil. Reduce heat; simmer, uncovered, for 5-6 minutes or until mixture is thickened and sugar is completely dissolved. Spread over crackers.
Bake at 350° for 7-8 minutes or until bubbly. Sprinkle with chips. Bake 3-5 minutes longer or until chips begin to melt; spread chocolate evenly over top.
Chill for 15-20 minutes or until set; break into pieces. Store in the refrigerator. Yield: about 1-3/4 pounds.