3/4 c Sugar 2/3 c Golden brown sugar 1/2 c Unsalted butter; room temp. 2 ea Large egg whites 1 1/2 t Vanilla extract 1 1/4 c Peanut butter, chunky* 1 c All-purpose flour 1/2 t Baking soda 1/4 t Salt 5 ea 2.1-ounce Butterfinger bars* *NOTE: Do not use freshly ground or "old-fashioned style" peanut butter. Butterfinger bars should be cut into 1/2-inch pieces. Preheat oven to 350F. Lightly grease 2 cookie sheets. STEEL KNIFE:(Food Processor recipe) Blend sugars, butter, egg whites and vanilla until fluffy, stopping once to scrape down sides of work bowl, about 1 minute. Add peanut butter and process until combined, about 20 seconds. Add flour, baking soda and salt and blend until just combined using 2 to 3 on/off turns; do not overprocess. Transfer to large bowl. Stir in chopped Butterfingers. Mound dough by 1 1/2 tablespoonfuls onto prepared sheets, spacing 2 inches apart. Flatten slightly using fingers. Bake until dry in appearance and centers are still slightly soft to touch, about 15 minutes. Cool on cookie sheets 3 minutes. Transfer to rack and cool completely. Store in airtight container. (Can be prepared ahead. Store 4 days at room temperature or freeze 3 weeks.)