Cover bottom of a 13- x 9-inch aluminum foil-lined pan with crackers.
Microwave butter and brown sugar in a microwave-safe glass bowl on HIGH for 3 to 4 minutes or until sugar dissolves, stirring occasionally. Pour butter mixture over crackers.
Bake at 325° for 15 minutes or until bubbly. Remove from oven, and sprinkle with chocolate morsels, spreading as they melt. Sprinkle with pecans.
Cover and chill at least 2 hours. Cut toffee into 1-inch squares or break into pieces, and store in an airtight container in refrigerator.