PREHEAT oven to 425° F. Line 15 x 10-inch jelly-roll pan with heavy-duty foil.
MELT 1/4 cup (1/2 stick) butter in medium saucepan. Pour into prepared jelly-roll pan. Arrange crackers over butter, breaking crackers to fit empty spaces.
MELT remaining butter in same saucepan; add sugar. Bring to a boil over medium heat. Reduce heat to low; cook, stirring occasionally, for 2 minutes. Remove from heat; stir in sweetened condensed milk. Pour over crackers.
BAKE for 10 to 12 minutes or until mixture is bubbly and slightly darkened. Remove from oven; cool for 1 minute.
SPRINKLE with morsels. Let stand for 5 minutes or until morsels are shiny; spread evenly. Sprinkle with nuts; press into chocolate. Cool in pan on wire rack for 30 minutes. Refrigerate for about 30 minutes or until chocolate is set. Remove foil; cut into pieces.