IN A HEAVY SAUCEPAN, COMBINE CHOCOLATE CHIPS, SWEETENED CONDENSED MILK, AND MARSHMALLOWS OVER MEDIUM HEAT, AND STIR CONSTANTLY UNTIL MIXTURE IS SMOOTH.

REMOVE FROM HEAT, STIR IN VANILLA, WALNUTS, AND SALT.

POUR MIXTURE INTO AN 8" X 8" PAN LINED WITH WAX PAPER.

REFRIGERATE FOR 2 HOURS, OR UNTIL FIRM.

CUT INTO SQUARES.