PREHEAT OVEN TO 150ºC . IN A MEDIUM BOWL, COMBINE FLOUR, SODA AND SALT. MIX WELL AND SET ASIDE. IN A LARGE BOWL WITH AN EXLECTRIC MIXER, BLEND SUGARS AT MEDIUM SPEED. ADD BUTTER AND MIX TO FORM A GRAINY PASTE, SCRAPING DOWN THE SIDES OF THE BOWL. ADD EGG, LIQUEUR AND BANANA, AND BEAT AT MEDIUM SPEED UNTIL SMOOTH. ADD THE FLOUR MIXTURE, 1 CUP OF THE CHOCOLATE CHIPS AND THE WALNUTS AND BLEND AT LOW SPEED UNTIL JUST COMBINED. DROP BY ROUNDED TABLESPOONS ONTO UNGREASED COOKIE SHEETS, 5 cm APART. SPRINKLE COOKIES WITH CHOCOLATE CHIPS, 6 TO 8 PER COOKIE. BAKE 25-27 MINUTES UNTIL COOKIE EDGES BEGIN TO BROWN. TRANSFER IMMEDIATELY TO A COOL SURFACE.