Preheat oven to 350 degrees. Lightly grease cookie sheets. In food processor with steel knife; Blend sugar, butter, and egg yolks until fluffy, stopping once to scrape down sides of bowl, about 1 minute. Add flour, salt, and nuts and process until just combined using on/off turns. Don't overprocess. Transfer to a large bowl and stir in chocolate and butterscotch chips. Mound dough by 2 tablespoon. (I made mine slightly smaller) onto prepared sheets, spacing 2" apart. Flatten slightly using fingers. Bake until dry in appearance and centers are still slightly soft to touch, about 20 minutes (mine were done in 14-15). Cool on sheets for 3 minutes; transfer to a wire rack to cool completely. Store in airtight container. I sure hope you like them!