BLEND BUTTER, SUGARS, EGG,AND VANILLA UNTIL FLUFFY, STOPPING ONCE TO SCRAPE DOWN SIDES OF BOWL, ABOUT 1 MIN. ADD FLOUR,BAKING SODA AND SALT AND MIX UNTIL JUST COMBINED. DO NOT OVER MIX. STIR IN WHITE CHOCOLATE CHUNKS AND NUTS. MOUND DOUGH BY one third CUPFULS ONTO LIGHTLY GREASED COOKIE SHEET, SPACE ABOUT 2 IN. APART. BAKE IN PREHEATED 375 DEGREE OVEN UNTIL LIGHLY BROWN AROUND EDGES, ABOUT 15 MIN.COOL ON COOKIE SHEET FOR 3 MIN, THEN REMOVE TO RACKS AND COOL COMPLETLEY. STORE IN AIR-TIGHT CONTAINER. (CAN BE PREPARED AHEAD. STORE COOKIES UP TO 4 DAYS AT ROOM TEMP. OR FREEZE 3 WKS.)