In a mixing bowl, cream butter and sugars.
Add egg and vanilla; beat until light and fluffy.
Combine dry ingredients; beat into creamed mixture.
Divide dough in half; place each half between two sheets of waxed paper.
Roll into 12-in.x 10-in.rectangles.
Chill until almost firm, about 30 minutes.
In a saucepan over low heat, melt chips and butter.
Add vanilla and salt; mix well.
Spread over dough.
Carefully roll up each rectangle into a tight jelly roll; wrap in waxed paper.
Chill for 2 hours or until firm.
Cut into 1/8-in.slices with a sharp thin knife; place on greased or parchment-lined baking sheets.
Bake at 350° for 7-10 minutes or until lightly browned.
Cool on wire racks.