Recalls Elizabethtown, Pennsylvania field editor Patricia Kile, "My husband's 95-year-old grandfather was intrigued with how the swirls got in these cookies!"
In a large bowl, cream butter and sugars until light and fluffy. Beat in egg and vanilla. Combine the dry ingredients; gradually add to creamed mixture and mix well.
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 microwave-safe bowl, melt chips and butter; stir until smooth. Beat in vanilla and salt. Spread over dough. Carefully roll up each rectangle into a tight jelly roll, starting with the long side. Wrap in waxed paper. Chill for 2 hours or until firm.
Gently cut into 1/2-in. slices with a sharp serrated knife; place on greased or parchment-lined baking sheets. Bake at 350° for 10-12 minutes or until lightly browned. Cool on wire racks.
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