COARSELY CHOPPED PREHEAT OVEN TO 300* F. IN A MEDIUM BOWL COMBINE FLOUR, SODA AND SALT MIX WELL AND SET ASIDE. IN A LARGE BOWL WITH AN ELECTRIC MIXER BLEND SUGARS AT MEDIUM SPEED. ADD BUTTER AND MIX TO FORM A GRAINY PASTE, SCRAPING DOWN THE SIDES OF BOWL. ADD EGGS AND VANILLA AND BEAT AT MEDIUM SPEED UNTIL LIGHT AND FLUFFY. ADD THE FLOUR MIXTURE, PECANS AND WHITE CHOCOLATE AND BLEND ON LOW SPEED UNTIL JUST COMBINED. DROP BY ROUNDED TABLESPOONS ONTO UNGREASED COOKIE SHEETS, 2 INCHES APART. BAKE 20-22 MIN. OR UNTIL EDGES JUST BEGIN TO TURN GOLDEN BROWN. TRANSFER COOKIES TO A COOL FLAT SURFACE.