Blondie's Grandma K's Cookies

Preheat oven to 350°F.

In medium bowl, cream butter and sugars; add egg yolk.

Add flour; mix well.

Roll dough into 1 inch balls; place on greased cookie sheets.

Flatten each ball crosswise with fork lightly dipped in flour.

Sprinkle with colored sugar or jimmies (sprinkles).

Bake at 350°F for 10 to 12 minutes or until lightly browned. Cool on wire cooling racks.